Clutch unit

ABSTRACT

A clutch unit comprises an outer ring  1  as an input-side member, an output shaft  2  as an output-side member, an inner ring  3  as a control member, an outer ring  4  as a stationary-side member, a first clutch part  5  interposed between the outer ring  1  and the inner ring  3   m , and a second clutch part  6  interposed between the outer ring  4  and the output shaft  2 . Input torque input from an operation lever  13  is transmitted in the path of the outer ring  1 →the first clutch part  5 →the inner ring  3 →the output shaft  2 . Reverse input torque input from the output shaft  2  is locked with the outer ring  4  through the second clutch part  6.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a clutch unit which has thefunction of transmitting input torque from an input side to an outputside and locking reverse input torque from the output side so as not toflow back to the input side, and is applicable to a seat-adjustingdevice of a vehicle, for example.

[0002] For example, for a device in which an input torque given by arotating operation of an operation member is transmitted to anoutput-side mechanism to adjust a position of a predetermined part, afunction for holding the position of the output-side mechanism is oftenrequired when the operation member is not operated. Taking aseat-height-adjusting device for a sitting seat of a vehicle, forexample, the device comprises a brake part for supporting the weightfrom the sitting seat including the weight of the seat itself and theweight of the driver and the like, provided at an output-side mechanism,wherein a normal or a reverse input torque is input from an operationmember to an input shaft of the brake part to adjust the height positionof the sitting seat. The height position of the sitting seat is held bythe brake part even when the operation member is released. Thus, theabove function is performed. In this case, since the position of theoperation member is held by the brake part after the operation, a knob(or a circular grip) is commonly used as the operation member, and theinput torque is input to the brake unit by the rotating operation of theknob.

[0003] The seat-height-adjusting device of the prior art requiresinconvenient operation of rotating the knob while the driver inserts hishand in a narrow space between the sitting seat and the vehicle body.Also, the necessity to secure such space imposes limits to the design ofthe vehicle body and the seat, which can be a burden particularly forsmall vehicles. Another known seat-height-adjusting device employs alever as the operation member, with a ratchet mechanism between thelever and the brake part so as to enable to input a torque by a pivotingoperation of the lever and to automatically return the lever afteroperation. However, this device requires a complex structure, and alsohas the problem of noise generated by toothed ratchet gears when thelever returns.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a clutch unitwhich can achieve the position adjustment and the position hold of anoutput-side mechanism and the position return of an input member(operating member), and also has a simple structure, and is smooth inoperation.

[0005] Another object of the present invention is to provide a clutchunit that is compact, low-cost, and capable of improvement in designflexibility.

[0006] Still another object of the present invention is to provide aclutch unit that can prevent clutch function thereof from being impairedby thermal deformation of components during processing and the usedgrease from deteriorating due to heat, can facilitate the process andmanufacturing, and can be mounted on a mating member without trouble.

[0007] Still another object of the present invention is to provide aclutch unit that is high in durability and excellent in assemblability.

[0008] Still another object of the present invention is to smoothen theshift performance of the locking means from a locked state to a lockreleased state, thereby reducing the operating force and suppressing theproduction of vibrations and vibrating noise.

[0009] To achieve the foregoing objects, the present invention providesa structure comprising an input-side member to which a torque is input,an output-side member from which a torque is output, a control memberintervening in a torque transmission path between the input-side memberand the output-side member, a stationary-side member constrained fromrotation, a first clutch part arranged between the input-side member andthe control member, and a second clutch part arranged between thestationary-side member and the output-side member, wherein an inputtorque from the input-side member is transmitted to the output-sidemember through the first clutch part and the control member, and areverse input torque from the output-side member is locked with thestationary-side member through the second clutch part. According to thisstructure, it is possible to adjust the position of the output-sidemember in the direction of rotation by the input torque from theinput-side member. In addition, since the reverse input torque from theoutput-side member is locked by the second clutch part, the adjustedposition of the output-side member can be held. Moreover, since thefirst clutch part is arranged between the input-side member and thecontrol member, the input-side member can be returned to its neutralposition (the position at which the input torque being not input) afterthe position adjustment of the output-side member. Even in that case,the smooth returning operation causes no problem of noise generation aswith a ratchet mechanism.

[0010] In the above structure, the first clutch may include lockingmeans for locking the input-side member and the control member withrespect to the input torque from the input-side member, and returningmeans for returning the input-side member to a neutral position at whichthe input torque is not input when the input-side member is released.According to this structure, when the input-side member is releasedafter the position adjustment of the output-side member, the input-sidemember returns automatically to the neutral position by the returningmeans. Thus the operationality is improved.

[0011] The locking means includes any of those which gives constrainforce of rotation by utilizing wedging engagement, projection-recessengagement, friction, magnetic force, electromagnetic force, fluidpressure, fluid viscous resistance, or fine particle medium. Among them,the locking means giving constrain force of rotation by wedgingengagement is preferable because the advantages of simplicity ofstructure and control mechanism, smoothness of motion, and low cost andthe like. More specifically, in a preferred embodiment, wedge gaps aredefined between the input-side member and the control member, andengaging members are made come into and out from wedging engagementswith the wedge gaps, thereby switching a locked state and a freewheelingstate. This structure includes the arrangements in which cam surfacesfor defining the wedge gaps may be formed to the input-side member or tothe control member, with each of the engaging members having a circularcross-section such as rollers or balls, and cam surfaces for definingthe wedge gaps are formed to the engaging members, with each of theengaging members being a sprag or the like having a non-circularcross-section.

[0012] More preferably, the locking means may comprise cam surfacesprovided to the input-side member, a circumferential surface provided tothe control member, engaging members interposed between the cam surfacesand the circumferential surface. The returning means may comprise aretainer for retaining the engaging members, and an elastic member forcoupling the retainer with a non-rotary member in the direction ofdirection.

[0013] With the structure described above, when an input torque is inputto the input-side member, the cam surfaces of the input-side memberrelatively moves in the direction of rotation with respect to theengaging members accompany with the rotation of the input-side member,thereby, the engaging members come into engagements with the wedge gaps.Thus, the input torque from the input-side member is transmitted to thecontrol member through the engaging members, so that the input-sidemember, the engaging members, the retainer, and the control member allrotate together. The rotation of the retainer causes the elastic member,which couples the retainer with the non-rotary member in the directionof rotational, to deform, generating an elastic force in accordance withthe amount of deformation. Therefore, when the input-side member isreleased after rotating a certain amount, this elastic force accumulatedin the elastic member acts as a rotational driving force on theretainer, whereupon the retainer pushes the engaging members against thecam surface. Thereby, the engaging members, the retainer, and theinput-side member freewheel with respect to the control member to returnto the neutral position.

[0014] In the structure described above, the non-rotary member withwhich the retainer is coupled through the elastic member may be thestationary-side member, so as to simplify the structure. Further, astopper may be provided to the stationary-side member for restrictingthe rotation range of the input-side member, so that the elastic memberwill not receive too much stress because of excessive rotation of theinput-side member and also the structure can be simplified. Furthermore,the engaging members, the retainer, and the elastic member may all beaccommodated inside of the input-side member, so as to make an inputside portion compact without any protruding parts. This eliminates thedisadvantage that any protrusions on the input side portion may biteinto the cloth on the surface of the seat when operating the operationmember, and improves the freedom of design of the seat, in such casethat the clutch unit is uses to a seat-adjusting device of a vehicle. Inaddition, the cum surfaces of the input-side member may be formed insuch a shape that defines the wedge gaps together with thecircumferential surface of the output-side member in both normal andreverse directions of rotation. Thereby, the above function can beobtained with respect to the input torque in both normal and reversedirections. Incidentally, the cam surfaces may be formed to theinput-side member directly, or a member having the cam surfaces may beattached to the input-side member. Moreover, the engaging member ispreferably a roller.

[0015] The second clutch part may comprise locking means for locking theoutput-side member and the stationary-side member with respect to thereverse input torque from the output-side member, lock releasing meansfor releasing a locked state due to the locking means with respect tothe input torque from the input-side member, and torque transmittingmeans for transmitting the input torque between the control member andthe output-side member when the locked state due to the locking means isreleased. According to this structure, the position adjustment of theoutput-side member in the direction of rotational can be performed by aninput operation of the input torque from the input-side member, and alsothe position of the output-side member after adjusting can beautomatically held. Thus the operationality is improved.

[0016] The locking means includes any of those which gives constrainforce of rotation by utilizing wedging engagement, projection-recessengagement, friction, magnetic force, electromagnetic force, fluidpressure, fluid viscous resistance, or fine particle medium. Among them,the locking means giving constrain force of rotation by wedgingengagement is preferable because the advantages of simplicity ofstructure and control mechanism, smoothness of motion, and low cost andthe like. More specifically, in a preferred embodiment, wedge gaps aredefined between the output-side member and the stationary-side member,and engaging members are made come into and out from wedging engagementswith the wedge gaps, thereby switching a locked state and a freewheelingstate. This structure includes the arrangements in which cam surfacesfor defining the wedge gaps may be formed to the output-side member orto the stationary-side member, with each of the engaging members havinga circular cross-section such as rollers or balls, and cam surfaces fordefining the wedge gaps are formed to the engaging members, with each ofthe engaging members being a sprag or the like having a non-circularcross-section.

[0017] More preferably, the locking means may comprise a circumferentialsurface provided to the stationary-side member, cam surfaces provided tothe output-side member for defining wedge gaps together with thecircumferential surface in both normal and reverse directions ofrotational, a pair of engaging members interposed between each of thecam surfaces and the circumferential surface, and elastic members eachof which presses the pair of engaging members toward the respectivewedge gaps. The lock releasing means may comprise engaging elements forselectively engaging with either one of the pair of engaging members topress the engaging member toward the opposite direction to the wedgegap. The torque transmitting means may comprise engaging elements in thedirection of rotation provided to the control member and the output-sidemember.

[0018] In the structure described above, when a reverse input torque inone direction of rotation is input to the output-side member, one of thepaired engaging members comes into wedging engagement with the wedge gapin that direction, thereby locking the output-side member in the onedirection of rotational with respect to the stationary-side member. Whena reverse input torque in the other direction of rotation is input tothe output-side member, the other of the paired engaging members comesinto wedging engagement with the wedge gap in that direction, therebylocking the output-side member in the other direction of rotational withrespect to the stationary-side member. Thus, the output-side member islocked with respect to the stationary-side member through the pair ofengaging members in both normal and reverse directions of rotational. Onthe other hand, when an input torque is input to the input-side member,the engaging element of the lock releasing means initially pushes one ofthe paired engaging members engaging with the wedge gap in the directionof rotation of the input torque towards the opposite direction of thewedge gap, so as to make the engaging member come out from the wedgegap. The locked state of the output-side member is thus released in thedirection of rotation of the input torque. Then, under the locked stateof the output-side member being released, the engaging elements providedto the control member and the output-side member engage with each otherin the direction of rotation. Thereby, the input torque input to theinput-side member is transmitted along a path from the input-side memberthrough the first clutch part, the control member, the torquetransmitting means (engaging elements), to the output-side member, sothat the output-side member rotates.

[0019] In order to perform the lock release due to the lock releasingmeans and the torque transmission due to the torque transmitting meanssurely and sequentially, the lock releasing means and the torquetransmitting means in the neutral position may have a positionalrelationship of δ1<δ2, where δ1 is a rotational direction clearancebetween the engaging element of the lock releasing means and theengaging member, and δ2 is a rotational direction clearance between theengaging elements of the torque transmitting means. The lock releasingmeans may be provided to the control member because the advantages ofsimplicity of structure and control mechanism. Further, the torquetransmitting means may be constituted by projections provided to eitherone of the control member and the output-side member, and matchingrecesses provided to the other one. More specifically, the projectionsmay be pins provided to the control member, and correspondingly, therecesses may be pin holes provided to the output-side member. In thiscase, the pins and the pin holes may be formed along the clutch axis.The cam surfaces may be directly formed to the output-side member, or aseparate member having cam surfaces may be attached to the output-sidemember. For the engaging members, rollers are preferable.

[0020] In the structure described above, a radial bearing may beprovided for radially supporting the output-side member, so as to makethe rotary motion of output-side member smooth and stable, and toprevent or restrict eccentric load from being applied to the firstclutch part or the second clutch part. The radial bearing may beconstructed by a separate rolling bearing or slide bearing, butpreferably, a radial bearing portion may be provided to the controlmember, or to a fixing side plate fixed to the stationary-side member,in order to simplify the structure and reduce the number of components.More preferably, the radial bearings may be provided to both of thecontrol member and the fixing side plate so that the output-side memberis supported in a state of straddle by the radial bearing portions,whereby the above-mentioned effects are achieved with a better result.

[0021] As described above, the output-side member is locked with respectto the reverse input torque by the second clutch part. However, at themoment when the locked state due to the second clutch is released withrespect to the input torque, the reverse input torque could possiblyflow back to the input side through the torque transmitting means. Suchflow back phenomenon of the reverse input torque may take the form ofresistance against the operation of the operation member, or a suddendrop of the seat. Accordingly, the clutch unit may further comprisebrake means for applying a braking force on the output-side member inthe direction of rotational, so as to prevent or restrict such flow backphenomenon of the reverse input torque. The braking force mentioned hereincludes friction, magnetic force, electromagnetic force, fluidpressure, fluid viscous resistance, or the like.

[0022] The brake means may be interposed between the output-side memberand the stationary-side member or the fixing side plate fixed to thestationary-side member. The brake means may be constituted by a frictionmember for applying frictional force as the braking force on theoutput-side member.

[0023] According to the present invention, it is possible to provide aclutch unit that can achieve the position adjustment and the positionhold of the output-side mechanism and the position return of theinput-side member (operation member), has a simple structure, and issmooth in operation.

[0024] In the foregoing structure, the elastic member for coupling theretainer with a non-rotating member in the direction of rotation, asshown in FIG. 38, for example, may be a centering spring Xa made of anunwinding type torsion coil spring having a plurality of turns. Then,engaging portions Xa1 and Xa2 are formed at both ends of the centeringspring Xa. In a natural state shown in the figure, the centers of theplurality of turns fall on the same axis.

[0025] When the centering spring Xa is installed in the first clutchpart, as shown in FIG. 38(c), the pair of engaging portions Xa1 and Xa2both are engaged with an engaged portion Xb of the retainer and anengaged portion Xc of the stationary-side member respectively as widenedin the unwinding direction. Under this state, the individual windingcenters of the centering spring Xa shift in succession due to thewidening.

[0026] From such a state, when the retainer (the engaged portion Xb) isrelatively rotated with respect to the stationary-side member (theengaged portion Xc), as shown in FIG. 38(d), the individual windingcenters of the centering spring Xa increase in the amount of shift.Accordingly, the centering spring Xa might expand outward at near theengaging portion Xa1, for example, to make contact with the input-sidemember Xd (the outer ring at the operating member side).

[0027] In order to avoid this problem, the space for accommodating thecentering spring Xa must be expanded. Thus, the first clutch part couldincrease in size, with the fear of hindrance to achieving a compactclutch unit. This also results in the fear of narrowing the design rangeof the clutch unit which is the first clutch part and the second clutchpart unitized.

[0028] Incidentally, the use of a winding type centering spring Ya asshown in FIG. 39 has been attempted on this account. When this centeringspring Ya is installed in the first clutch part, however, a pair ofengaging portions Ya1 and Ya2 are engaged with an engaged portion Yb ofthe retainer and an engaged portion Yc of the stationary-side member aswidened in the winding direction as shown in FIG. 39(b). Thus, thecentering spring Ya decreases in diameter while the individual windingcenters shift in succession due to the foregoing widening.

[0029] When the retainer is relatively rotated from such a state, thecentering spring Ya further decreases in diameter while the individualwinding centers increase in the amount of shift. Consequently, thecentering spring Ya might constrict the retainer, sometimes failing toprovide the expected clutch function. In order to avoid this problem,the first clutch part must be expanded as in the case mentioned above,with the fears of hindrance to achieving a compact clutch unit and of anarrower design range.

[0030] The foregoing problem can be solved by making the centeringspring as the elastic member to be arranged in the first clutch part,out of a torsion coil spring having a plurality of turns, and offset theindividual winding centers of the torsion coil spring in a natural stateto an opposite direction from a direction in which the individualwinding centers shift accompany with increase in the amount of operationof the retainer in an assembled state.

[0031] According to such structure, when the retainer is operated(relatively rotated) with the centering spring made of the torsion coilspring having a plurality of turns installed in the clutch part, theindividual winding centers of the centering spring shift to apredetermined direction accompany with the increasing amount ofoperation (relative rotational angle). In this case, the individualwinding centers of the centering spring in the natural state are offsetin the opposite direction from the foregoing predetermined direction.When the retainer is in operation, the individual winding centerstherefore decrease in the amount of shift as much as corresponding tothe offset. Consequently, the clutch part can be reduced in the diameterof the space for accommodating the centering spring, so that a compactclutch unit is achieved with enhanced design flexibility.

[0032] The individual winding centers of the centering spring describedabove preferably fall on the same axis when the retainer in theassembled state is not in operation. If so, the individual windingcenters of the centering spring shift in both directions evenly with anefficient reduction in the amount of shift regardless of whether thedirection of operation (the direction of relative rotation) of theretainer is normal or reverse.

[0033] The centering spring described above is preferably an unwindingtype spring. This prevents the centering spring from decreasing indiameter. Consequently, even if a centering spring having a smalldiameter is arranged around the retainer, the centering spring will notconstrict the retainer to hinder the clutch function. The centeringspring is thus reduced in diameter.

[0034] Moreover, the centering spring described above is preferablyshaped noncircular in section. That is, because of the noncircular shapewhich offers higher spring rigidity than circular one having the sameinner and outer diameters, an operation lever attached to the input-sidemember can be maintained with a sufficient strength, for example. Inparticular, when the centering spring is shaped rectangular in section,the torsion torque can be changed by modifying the outer diameter alone,even with the same inner diameter and width. This allows flexiblemeasures for setting modifications to the necessary torsion torque.

[0035] Furthermore, the centering spring described above is preferably aso-called pitched spring which is wound with spacing between turns. Thatis, if a so-called tight spring having no spacing between turns is used,the necessary torsion force or return force may not be attained due tofriction loss occurring between the turns. The use of the pitched springcan avoid such a problem.

[0036] The fixing side plate may be fixed to the stationary-side memberby welding or by screwing. In the case of welding, however, there arethe problems that the manufacturing cost becomes higher, thestationary-side member causes thermal deformation to impair the clutchfunction, and the used grease deteriorates. Moreover, in the case ofscrewing, there are the problems that: the stationary-side member, whichinvolves in the clutch function, has a higher hardness, being difficultto form holes such as screw holes and taking a lot of trouble and timefor machining and fabrication; and screw heads, nuts, or the likeprotruding on the back of the fixing side plate can cause trouble inmounting on a seat-side member.

[0037] The problems mentioned above can be solved by the adoption of thestructure that the fixing side plate is fixed to the stationary-sidemember by caulking. The adoption of such structure lowers the processingand manufacturing costs, and precludes such problems as the impairedclutch function resulting from thermal deformation and the deteriorationof the used grease as might occur in welding. Besides, the caulking canbe conducted without unnecessary protrusions on the back of the fixingside plate. The clutch unit can thus be mounted on a mating member (aseat-side member, for example) via the fixing side plate withoutobstructive portions, thereby allowing sure and appropriate mounting.

[0038] As for the method of caulking, a caulking portion formed on thefixing side plate is preferably bent for the caulking to thestationary-side member. This structure can facilitate the caulking work,and ensure a fixed state to eliminate such problems as slip-off orcoming-off.

[0039] The caulking portion of the fixing side plate is preferably bentin the circumferential direction of the stationary-side member. That is,if the caulking portion is bent in the radial direction of thestationary-side member, the stationary-side member might sufferdeformation under radial stress and the deformation could hinder thenormal operation of the second clutch part. In contrast, when thecaulking portion is bent in the circumferential direction of thestationary-side member, the absence of radial stress makes thestationary-side member less prone to deformation so that the clutchfunction of the second clutch part can be maintained normal.

[0040] Moreover, the caulking portion of the fixing side plate ispreferably bent to the stationary-side member so as to be restrainedfrom circumferential movement. According to such structure, simplybending the caulking portion achieves restraint on both the axialmovement and circumferential movement of the fixing side plate withrespect to the stationary-side member. This not only ensures the fixedstate, but also simplifies the work and improves the working efficiency.

[0041] In this case, the stationary-side member preferably has a notchin an outer periphery thereof so that the caulking portion is engagedwith the notch. According to such structure, bending the caulkingportion in engagement with the notch of the stationary-side memberrestrains the fixing side plate from axial movement and circumferentialmovement with respect to the stationary-side member.

[0042] Furthermore, the caulking portion of the fixing side platepreferably has a pair of tabs, the pair of tabs being bent in oppositedirections. According to such structure, both the axial movement andcircumferential movement of the fixing side plate with respect to thefixing side plate can be restrained with efficiency and reliability.

[0043] The notch and caulking portion described above are preferablyprovided to the stationary-side member and the fixing side plate at aplurality of circumferential locations, respectively. In this case, afixed state uniform all around can be obtained by arranging the notchesand the caulking portions at circumferential regular positions.

[0044] Then, the stationary-side member is preferably made of hardenedsteel, and the fixing side plate unhardened steel. That is, thestationary-side member is made of material having a higher hardnesssince it is involved in the clutch function. The fixed-side member ismade of material that allows the bending of the caulking portion(s).

[0045] When the clutch unit of the present invention is used in aseat-adjusting device of a vehicle, the fixing side plate preferably hasa second caulking portion intended for caulking to a seat-side member.According to such structure, the clutch unit can be mounted on a seat atlow cost without a complicated work.

[0046] In the structure described above, the elastic member of the firstclutch part may have a pair of engaging portions differing from eachother in axial position. The retainer may have a pair of engagedportions with which the engaging portions of the elastic member engaged,and pockets for retaining the engaging members. At least either one ofthe pair of portions may be axially thickened at a base part thereof.

[0047] With normal and reverse rotations of the retainer, the engagedportions of the retainer undergo a circumferential pressing force due toelastic deformation of the elastic member through the engaging portionsof the elastic member. Thus, excessive stress can act on the base partsof the engaged portions, possibly causing a crack or the like.Thickening the base part(s) of the engaged portion(s) can ensurestrength to avoid such a problem.

[0048] This thickening can be achieved, for example, by arranging thebottom of a notch making one of the engaged portions closer to an endface of the retainer than the bottom of a notch making the other engagedportion. In particular, the engaged portion of the retainer inengagement with one of the pair of engaging portions of the elasticmember lying closer to the end face of the retainer has a greater armlength to the position of engagement. Since its base part undergoes alarge moment load, the foregoing measures are effective.

[0049] Moreover, the other engaged portion may be thickened at the basepart thereof by omitting the pocket near the base part, or reducing theaxial dimension of the pocket near the base part. The engaged portion ofthe retainer in engagement with one of the pair of engaging portions ofthe elastic member lying closer to the center (axial center) of theretainer must have a deeper notch since the position of engagement withthis engaging part lies closer to the center of the retainer. This makesthe thickening with the depth adjustment of the notch difficult. Even inthat case, the base part of the engaged portion can be thickenedaccording to the present structure.

[0050] Moreover, in the foregoing structure, the elastic member of thesecond clutch part may be made of a plate spring having two bendingportions. This disperses the bends at the respective bending portions,as compared with the elastic member having a single bending portionalone. It is therefore possible to avoid plastic deformation of theplate spring in releasing the locked state of the second clutch part,thereby allowing the miniaturization of the plate spring and byextension the miniaturization of the clutch unit. Besides, the platespring will not be entangled mutually as coil springs are.

[0051] Specifically, the plate spring has a coupling portion forcoupling the two bending portions at one end each, and side plateportions extending from the other ends of both the bending portions. Inthis case, the plate spring has a generally N-shaped section, allowingarrangement even in a narrow space between the engaging members.

[0052] When this plate spring is used, the cam surface of theoutput-side member for defining the wedge gaps may be a flat surfaceover a portion for the plate spring to be mounted on. In the case of aplate spring having a single bending portion alone, mounting the same onthe cam surface would require that a mounting groove be formed in thecam surface. The plate spring having two bending portions isfreestanding, and thus the cam surface may be a flat surface having nogroove. Since the groove is omitted from the cam surface, it becomespossible to simplify the machining process of the output-side memberthrough the omission of the groove formation. The problem of stressconcentration near the groove can also be avoided.

[0053] Now, in the foregoing structure, the cam surface of theoutput-side member may be formed convex with two tapered surfaces.Consequently, an appropriate strut angle can be maintained while thespace for accommodating the elastic member arranged between the engagingmembers (spring space) is expanded circumferentially. The elastic memberthus improves in design flexibility. This facilitates theminiaturization of the clutch unit.

[0054] The tapered surfaces constituting the cam surface desirably havean inclined angle in the range of 1° and 5°. Besides, the strut angle ofthe second clutch part desirably falls within the range of 3° and 4.5°.At strut angles above 4.5°, it becomes difficult for the engagingmembers to engage into the wedge gaps, whereby the clutch function isimpaired. On the other hand, at strut angles below 3°, the engagingmembers undergo higher surface pressure with a drop in torque capacity.

[0055] Now, in the foregoing structure, the input-side member may beformed by connecting a first thin member and a second thin member witheach other so as to be incapable of relative rotation, the first thinmember having the cam surfaces for the first clutch part, the secondthin member to which an operating member for inputting a torque isconnected. Here, a “thin member” refers to a member having a thicknesssmaller than when the input-side member is integrally formed by coldforging or the like.

[0056] According to such structure, the input-side member is separatedinto two members as the first thin member and the second thin member tobe processed. This facilitates the processing and lowers themanufacturing cost as compared to the case of integral forming by coldforging or the like. Besides, the first thin member and the second thinmember have only to secure minimum thicknesses according to theirrespective roles. The absence of unnecessary portions such as ones inthe case of integral forming by cold forging or the like allows areduction in the weight of the input-side member and by extension theclutch unit. In addition, the first thin member has the cam surfaces fora component of the clutch part, while the second thin member has aconnecting portion for an operating member. The two members thus differin characteristic requirements such as rigidity or strength.Consequently, the first thin member and the second thin member may bemade different from each other in material, machining condition, orprocessing condition so that the characteristic requirements of both themembers can be met efficiently during processing, heat treatment, andthe like.

[0057] At least either one of the first thin member and the second thinmember is preferably of a press-formed product. That is, since the firstthin member is provided with the cam surfaces for constituting theclutch part, it must be high in rigidity or strength in order to provideappropriate clutch function. In contrast, the second thin member doesnot require so high rigidity or strength comparatively. Consequently,for example, the first thin member may be a press-formed product of asteel plate or the like while the second thin member is a press-formedproduct of other metal material or a resin-formed product or the like.With consideration given to the standardization of the materials andprocessing methods, the second member may also be a press-formed productof a steel plate or the like. Then, such structure provides significantadvantages including facilitated machining, lower fabrication cost, andlighter weight.

[0058] Moreover, the first thin member and the second thin member arepreferably connected by a depression-projection fitting structure. Thatis, either one of the first thin member and the second thin member isprovided with a projection and the other is provided with a depression.The projection is fitted into the depression to connect the two thinmembers with each other so as to be incapable of relative rotation. Thissecures favorable assemblability of the two thin members, allowing easyfabrication of the input-side member and easy disassembly as well.

[0059] Furthermore, it is preferable that either one of the first thinmember and the second thin member has a fitting tab, and the other has agroove portion for the fitting tab to be fit with. Such structure notonly improves the assemblability and disassemblability of the two thinmembers but also ensures favorable workability of the two thin members.

[0060] At least the cam surface of the first thin member is preferablyapplied with a surface hardening. In such structure, the cam surface,which requires high-hardness characteristic as compared to otherportions of the second thin member and the first member, is given arequired hardness through the surface hardening such as heat treatment.A favorable clutch function can thus be maintained for a long term.

[0061] In the case where a torsion coil spring is used as the elasticmember of the first clutch part, when torsional forces incircumferential opposite directions are applied to both ends thereof,the elastic force acts on a member for supporting the elastic force (forexample, the retainer for retaining the engaging members) in the form ofa moment force since the torsion coil spring has a length in the axialdirection. Consequently, the member such as the retainer can cause aneccentricity or tilt to produce a friction with a peripheral member, sothat a lack of torsional torque may occur due to the frictional loss atthat time. This problem can be solved by making the elastic member ofthe first clutch part out of a plate spring of cut ring shape. That is,when a plate spring of cut ring shape is used as the elastic member,even if a torsional torque is applied to the elastic member with therotation of the input-side member, the point of application of theelastic force will not shift in axial position as with the torsion coilspring. Consequently, the member for supporting the elastic force, suchas the retainer, is kept from a moment force. This can suppress theeccentricity, tilt, and the like of the member, thereby minimizing thetorque loss resulting from the friction with other member.

[0062] In the foregoing structure, engaging portions capable ofengagement with the retainer and the stationary-side member,respectively, are desirably formed on both ends of the elastic member.In this case, the engaging portions on one end and the engaging portionson the other end can be arranged in circumferential opposite positionsto avoid a moment force resulting from the release of the elastic force.Besides, the retainer desirably has openings capable of engagement withthe engaging portions of the elastic member and being closed all around.Since the openings for engagement with the elastic member are shapedclosed all around (window-like shape), the retainer can be enhanced inrigidity as compared to the case where notches are formed in an end faceof the retainer.

[0063] Moreover, when stress adjusting portions are arranged near bothends of the elastic member, it is possible to uniformize the stressdistribution inside the elastic member after elastic deformation, andavoid a drop in fatigue life or the like due to unbalanced stressdistribution.

[0064] In addition, when a lamination of two or more plate springs isused as the elastic member, an arbitrary elastic force can be obtainedby changing the number of plate springs. This facilitates securing anelastic force conforming to the use condition, application, and thelike. In this case, when inner one of the plate springs is bent acute atboth ends to form engaged portions, and both ends of outer one of theplate springs are engaged with the engaged portions, the outer one ofthe plate springs can be surely prevented from shifting in phase orcoming off due to the action of external forces.

[0065] In the foregoing structure, a lubricating grease whose base oilhas a viscosity of 750 cSt or above may be applied to at least theinterior of the second clutch part including the locking means.

[0066] Here, the viscosity of 750 cSt is a value at 25° C. (in thisspecification, base oil viscosities will all be shown in values for 25°C.). In general, a base oil of lubricating grease for use in this typeof clutch has viscosity of 100 cSt or so. When the viscosity of the baseoil is equal to or greater than 750 cSt, the lubricating grease enhancesin the power for oil film formation so that lubricating oil films ofgreater oil film strength and oil film thickness are formed around thelocking means. This lowers the frictional resistance to a slip when thelocking means shifts from a locked state to a lock released state. Inaddition, the increased oil film strength and oil film thickness enhancethe effect of relieving a vibration impact. As a result, the shiftoperation of the locking means is smoothened, which reduces theoperating force and suppresses the occurrence of vibrations andvibrating noise on the shift motion.

[0067] A solid lubricant or an extreme pressure additive may be added tothe lubricating grease. Consequently, the frictional resistance can bereduced further to enhance the foregoing effect. The solid lubricant maybe PTFE or graphite, and the extreme pressure additive may be molybdenumdisulfide or organic molybdenum, for example.

[0068] When rollers are used as the engaging members, their rollingcontact surfaces may be given crowning. This suppresses edge load at thecontact portions with the rolling contact surfaces of the rollers,promoting the formation of oil films by the lubricating grease. Here,“crowning” refers to providing a slight curvature to the rolling contactsurface of a roller. It includes the structure that the rolling contactsurface is given curvatures at the areas of both ends, as well asso-called full crowning in which the entire rolling contact surfacetraces a single curvature. So-called cut crowning in which the crowningareas are drawn in straight lines (oblique lines) is also included. Whenthe rolling contact surface is given crowning at the areas of both ends,the amount of crowning (the axial length and the amount of radial dropof the crowning area) may differ between right and left. Moreover, whenthe rolling contact surface is given full crowning, the center ofcurvature of the crowning may be axially offset with respect to theaxial center position of the roller. Aside from the foregoing effect,the rolling contact surface of the roller becomes uneven in contactsurface pressure. It is therefore possible to generate a skew of theroller (a phenomenon in which the axis of the roller tilts with respectto the axis of the clutch) at the time of shift from the locked state tothe lock released state. Consequently, the wedge-engaged part(line-contact part) of the roller gradually comes out from one of theaxial ends to the other, with reduced frictional resistance during theshift motion. This smoothens the shift motion of the locking means,thereby reducing the operating force and suppressing the occurrence ofvibrations and vibrating noise during the shift motion. Otherwise, theskew generating means may use the structure that the rolling contactsurface of the roller and contact surface contact therewith are givensurface properties that differ between right and left with respect tothe axial center position of the roller. Specifically, it is possible tochange the surface roughness of the contact surface partially {forexample, apply dimpling (such as shot peening) partially}, or applyfriction reducing treatment to the contact surface (for example, applycoating for reducing friction, such as phosphate coating).

[0069] The clutch unit of the present invention is suitable for aseat-adjusting device of a motor vehicle. In that case, the input-sidemember is connected to an operation lever and the output-side member isconnected to a rotating member of the seat-adjusting device. Theseat-adjusting device here includes a seat-height-adjusting device foradjusting the height of a sitting seat, a seat-inclination-adjustingdevice for adjusting the inclination of a back seat, and aseat-slide-adjusting device for adjusting the front-and-back position ofa sitting seat. Of these, it is a seat-height-adjusting device of asitting seat that the clutch unit of the present invention isparticularly suitable for. According to this structure, the height ofthe sitting seat can be adjusted by operating the operation lever toswing. This can enhance operational convenience as compared toconventional device, and increase the design flexibility of the car bodyand the seat, being extremely useful to a seat-height-adjusting deviceof a compact car or a popular car in particular.

BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In the accompanying drawings:

[0071]FIG. 1 is a longitudinal cross-sectional view showing a clutchunit X according to one embodiment of the present invention;

[0072]FIG. 2(a) is a back side view, FIG. 2(b) is a longitudinalcross-sectional view, and FIG. 2(c) is a partial front view of an outerring serving as an input-side member;

[0073]FIG. 3(a) is a front view, and FIG. 3(b) is a longitudinalcross-sectional view of an output shaft serving as an output-sidemember;

[0074]FIG. 4(a) is a front view, and FIG. 4(b) is a longitudinalcross-sectional view of an inner ring serving as a control member;

[0075]FIG. 5(a) is a front view, and FIG. 5(b) is a longitudinalcross-sectional view of an outer ring serving as a stationary-sidemember;

[0076]FIG. 6(a) is a longitudinal cross-sectional view, and FIG. 6(b) isa front view of a fixing side plate;

[0077]FIG. 7(a) is a longitudinal cross-sectional view, and FIG. 7(b) isa front view of a friction member serving as brake means;

[0078]FIG. 8 is a cross-sectional view taken across the line BB of FIG.1, showing a first clutch part;

[0079]FIG. 9(a) is a front view, FIG. 9(b) is a longitudinalcross-sectional view, and FIG. 9(c) is a cross-sectional view of aretainer of the first clutch part;

[0080]FIG. 10(a) is a side view, and FIG. 10(b) is a front view of acentering spring of the first clutch part, and FIG. 10(c) is a diagramshowing the same when mounted;

[0081]FIG. 11 is an explanatory diagram illustrating the first clutchpart at a neutral position;

[0082]FIG. 12 is an explanatory diagram showing the first clutch partwhen a torque is transmitted;

[0083]FIG. 13 is an explanatory diagram showing the first clutch partwhen it is returned to the neutral position;

[0084]FIG. 14 is a cross-sectional view taken along the line A-A of FIG.1, showing a second clutch part;

[0085]FIG. 15 is a partial cross-sectional explanatory viewillustrating, to a larger scale, the second clutch part at a neutralposition;

[0086]FIG. 16 is a partial cross-sectional explanatory viewillustrating, to a larger scale, the second clutch part in an unlockingmotion;

[0087]FIG. 17 is a partial cross-sectional explanatory view illustratingthe second clutch part to a larger scale when a torque is transmitted;

[0088]FIG. 18 is a conceptual diagram showing a vehicle seat for anautomobile according to one embodiment of the present invention;

[0089]FIG. 19 is a conceptual diagram showing one example of a structurefor the seat-height-adjusting device;

[0090]FIG. 20(a) is a longitudinal cross-sectional view of a clutch unitY according to another embodiment of the invention, FIG. 20(b) is afront view of a friction member, and FIG. 20(c) is a cross-sectionalview of the friction member; and

[0091]FIG. 21(a) is a longitudinal cross-sectional view of a clutch unitZ according to yet another embodiment of the invention, FIG. 21(b) is afront view of a friction member, and FIG. 21(c) is a cross-sectionalview of the friction member.

[0092]FIG. 22 is a longitudinal sectional view showing a clutch unitaccording to a fourth embodiment of the present invention;

[0093]FIG. 23(a) is a longitudinal sectional view of an outer ring(input-side member), and FIG. 23(b) is a rear view of the same;

[0094]FIG. 24(a) is a longitudinal sectional view of an output shaft(output-side member), and FIG. 24(b) is a front view of the same;

[0095]FIG. 25(a) is a front view of an inner ring (control member), FIG.25(b) is a longitudinal sectional view of the same, and FIG. 25(c) is anenlarged view of essential parts of the same;

[0096]FIG. 26(a) is a front view of an outer ring (stationary-sidemember), and FIG. 26(b) is a longitudinal sectional view of the same;

[0097]FIG. 27(a) is a longitudinal sectional view of a fixing sideplate, and FIG. 27(b) is a front view of the same;

[0098]FIG. 28(a) is a longitudinal sectional view of a frictional member(braking means), and FIG. 28(b) is a front view of the same;

[0099]FIG. 29 is a B-B section of FIG. 1 showing a first clutch part;

[0100]FIG. 30 is a front view showing an operation lever;

[0101]FIG. 31(a) is a longitudinal section and front view showing aretainer of the first clutch part, FIG. 31(b) is a longitudinal sectionand side view of the same, and FIG. 31(c) is a rear view of the same;

[0102]FIG. 32(a) is a side view showing a natural state of a centeringspring of the first clutch part, FIG. 32(b) is a front view showing thenatural state of the same, FIG. 32(c) is a front view showing anassembled state of the same, FIG. 32(d) is a front view showing theoperation of the same, and FIG. 32(e) is an enlarged side view ofessential parts of the same;

[0103]FIG. 33 is an A-A section of FIG. 2 showing a second clutch part;

[0104]FIG. 34 is an enlarged partial front view showing the operation ofthe second clutch part (in a neutral position);

[0105]FIG. 35 is an enlarged partial front view showing the operation ofthe second clutch part (in releasing the lock);

[0106]FIG. 36 is an enlarged partial front view showing the operation ofthe second clutch part (during torque transmission);

[0107]FIG. 37(a) is a rear view showing another example of the innerring (control member), and FIG. 37(b) is a longitudinal sectional viewof the same;

[0108]FIG. 38(a) is a side view showing the natural state of a centeringspring of the first clutch part, FIG. 38(b) is a front view showing thenatural state of the same, FIG. 38(c) is a front view showing anassembled state of the same, and FIG. 38(d) is a front view showing theoperation of the same;

[0109]FIG. 39(a) is a front view showing the natural state of acentering spring of the first clutch part, and FIG. 39(b) is a frontview showing an assembled state of the same;

[0110]FIG. 40(a) is a longitudinal sectional view of essential partsshowing a fixed state of the outer ring (stationary-side member) and thefixing side plate, FIG. 40(b) is a front view of essential partsthereof, and FIG. 40(c) is a bottom view of essential parts thereof;

[0111]FIG. 41(a) is a longitudinal sectional view of essential partsshowing another example of the fixed state of the outer ring(stationary-side member) and the fixing side plate, FIG. 41(b) is afront view of essential parts of the same, and FIG. 41(c) is a bottomview of essential parts of the same;

[0112]FIG. 42(c) is a longitudinal sectional view of the retainer of thefirst clutch part, and FIG. 42(b) is an enlarged view of the area P of(a) FIG. 42(a);

[0113] FIGS. 43(a) and 43(b) are perspective views of the retainer ofthe first clutch part;

[0114]FIG. 44 is a perspective view of an elastic member for use in thesecond clutch part;

[0115]FIG. 45 is an enlarged partial cross-sectional view for explainingthe operation of the second clutch part;

[0116]FIG. 46 is an enlarged partial cross-sectional view for explainingthe operation of the second clutch part (with flat cam surfaces);

[0117]FIG. 47 is an enlarged partial cross-sectional view for explainingthe operation of the second clutch part (with tapered cam surfaces);

[0118]FIG. 48 shows an example where the input-side part alone isconfigured as an independent clutch unit, FIG. 48(a) being alongitudinal sectional view, FIG. 48(b) being a cross-sectional view;

[0119]FIG. 49 shows an example where the input-side part of a clutchunit according to a fifth embodiment is exclusively configured as anindependent clutch unit, FIG. 49(a) being a longitudinal sectional view,FIG. 49(b) being a cross-sectional view (B-B section);

[0120]FIG. 50(a) is a perspective view of a first thin member, FIG.50(b) is a longitudinal sectional view of the same, and FIG. 50(c) is afront view of the same;

[0121]FIG. 51(a) is a perspective view of a second thin member, FIG.51(b) is a longitudinal sectional side view of the same, and FIG. 51(c)is a front view of the same;

[0122]FIG. 52 is a perspective view showing the input-side member;

[0123]FIG. 53(a) is a side and front view showing a retainer of thefirst clutch part, FIG. 53(b) is a longitudinal section and side view ofthe same, and FIG. 53(c) is a front view of the same;

[0124]FIG. 54 is a longitudinal sectional view showing the entirestructure of the clutch unit according to the fifth embodiment;

[0125]FIG. 55(a) is a front view of an output shaft, and FIG. 55(b) is alongitudinal sectional view of the same;

[0126]FIG. 56(a) is a front view of an inner ring (control member), FIG.56(b) is a longitudinal sectional view of the same, and FIG. 56(c) is anenlarged view of essential parts of the same;

[0127]FIG. 57(a) is a front view of an outer ring (stationary-sidemember), and FIG. 57(b) is a longitudinal sectional view of the same;

[0128]FIG. 58(a) is a front view of a fixing side plate, and FIG. 58(b)is a longitudinal sectional view of the same;

[0129]FIG. 59(a) is a front view of a frictional member (braking means),and FIG. 59(b) is a longitudinal sectional view of the same;

[0130]FIG. 60 is a cross-sectional view of the first clutch part;

[0131]FIG. 61 is a cross-sectional view of the second clutch part;

[0132]FIG. 62 is a longitudinal sectional view showing the entirestructure of the clutch unit according to the second embodiment;

[0133]FIG. 63 is a perspective view of a retainer of the first clutchpart;

[0134]FIGS. 64 and 65 are perspective views of an elastic member of thefirst clutch part;

[0135]FIG. 66 is a front view for explaining the operation of theelastic member of the first clutch part, FIG. 66(a) showing a neutralstate, FIG. 66(b) showing a state where input torque is input;

[0136]FIGS. 67 and 68 are perspective views of the elastic member of thefirst clutch part;

[0137]FIG. 69 is a diagram showing the results of measurement on theoccurrence of vibrations during the operation of clutch units;

[0138]FIG. 70 is a diagram showing the relationship between the base oilviscosity of the lubricating grease and vibrations; and

[0139]FIG. 71 is a side view showing a roller of the second clutch part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0140] Preferred embodiments of the present invention will behereinafter described with reference to the accompanying drawings.

[0141]FIG. 1 shows the overall structure of a clutch unit according tothe first embodiment of the present invention. The clutch unit comprisesan outer ring 1 serving as an input-side member, an output shaft 2serving as an output-side member, an inner ring 3 serving as a controlmember, an outer ring 4 serving as a stationary-side member, a firstclutch part 5 interposed between the outer ring 1 and the inner ring 3,and a second clutch part 6 interposed between the outer ring 4 and theoutput shaft 2.

[0142]FIG. 2 shows the outer ring 1, which serves as an input-sidemember. The outer ring 1 has a plurality of protruding ribs 1 a and 1 b,for example three each, as in the illustrated example, at spacedintervals around the outer circumference thereof. One end portion of therib 1 a in its axial direction is divided into two by a recess 1 a 1,while the other end thereof extends from the end of the outer ring 1along the axis for forming a protrusion 1 a 2. Each of the ribs 1 b hasa screw hole 1 b 1 formed therein in the axial direction. The ribs 1 aand 1 b engage circumferentially with an operation lever 13 (see FIG. 1and FIG. 8) connected to the outer periphery of the outer ring 1,thereby preventing rotation of the operation lever 13 relative to theouter ring 1. The operation lever 13 is screw-held to the outer ring 1using the screw holes 1 b 1 in the ribs 1 b, so as not to move in theaxial direction relative to the outer ring 1. A centering spring 12, tobe described later with reference to FIG. 10, of the first clutch part5, is accommodated in the inner periphery of the protrusions 1 a 2. Theprotrusions 1 a 2 engage circumferentially with stoppers 4 a 1 of theouter ring 4, to be described later in detail with reference to FIG. 5,thereby restricting the rotation angle of the outer ring 1.

[0143] An inner periphery of the outer ring 1 at one end thereof isformed with a collar portion 1 c extending radially inwards. The collarportion 1 c is provided for the purpose of restrain a retainer 11 (seeFIG. 1 and FIG. 9) of the first clutch part 5, to be described later indetail, toward one side in the-axial direction, as well as maintainingthe coaxial relationship between the outer ring 1 and the inner ring 3.The outer ring 1 further has a plurality of, for example ten, equallyand circumferentially spaced cam surfaces 1 d along the inner peripherythereof. Each of the cam surfaces 1 d has a deepened center and twosurfaces slanting up toward both sides of the circumferential direction.

[0144] The outer ring 1 is, for example, forged with a steel materialsuch as steels for case hardening, carbon steels for machine structuraluse, or bearing steels, and then undergoes suitable heat treatment suchas carburizing and tempering, carbonitriding and tempering, inductionhardening and tempering, or dip quenching and tempering. In thisembodiment, steel for case hardening such as chromium-molybdenum steelSCM415 is employed for the outer ring 1, which is subjected tocarburizing and tempering as heat treatment, so that at least thesurface layer of the cam surfaces 1 d has a surface hardness of HRC57 to62. In this specification, HRC represents C scale of Rockwell hardness,and HV represents Vickers hardness. The outer ring 1 may also be of amachined product of a steel material, or a press-formed product of asteel plate such as a cold rolled steel sheet.

[0145]FIG. 3 shows the output shaft 2, which serves as an output-sidemember. The output shaft 2 comprises a journal portion 2 a on one end, alarge-diameter portion 2 a at the center, and a connecting portion 2 con the other end. The journal portion 2 a is inserted in a radialbearing surface 3 a 1 of the inner ring 3, to be described later indetail with reference to FIG. 4. The large-diameter portion 2 a isformed with a plurality of, for example eight, circumferentially equallyspaced cam surfaces 2 b 1 around the outer periphery thereof. Each ofthe cam surfaces 2 b 1 forms a flat surface, being a chord with respectto a circle of which center coincides with the axis of the output shaft2, and has an axially extending groove 2 b 2 formed in thecircumferential center thereof, in which a plate spring 21 of the secondclutch part 6, to be described later in detail with reference to FIG.14, is mounted. The large-diameter portion 2 a is formed, in one endthereof, with a plurality of (eight in this embodiment) axiallyextending pin holes 2 b 3, at spaced intervals in the circumferentialdirection. These pin holes 2 b 3 are provided for receiving pins 3 b 1of the inner ring 3, which will be described later with reference toFIG. 4. At the other end of the large-diameter portion 2 a is formedwith an annular recess 2 b 4, in which a friction member 9 (see FIG. 7),to be described later, is fitted. The annular recess 2 b 4 has an innercircumferential wall 2 b 5, which constitutes a journal surface insertedin a radial bearing surface 7 e 2 of a fixing side plate 7, which willbe described later with reference to FIG. 6. The connecting portion 2 cis formed with teeth 2 c 1 for connecting to other rotary member.

[0146] The output shaft 2 is, for example, forged with a steel materialsuch as steels for case hardening, carbon steels for mechanicalstructural use, or bearing steels, and then undergoes suitable heattreatment such as carburizing and tempering, carbonitriding andtempering, induction hardening and tempering, or dip quenching andtempering. In this embodiment, steel for case hardening such aschromium-molybdenum steel SCM415 is employed for the output shaft 2,which is subjected to carburizing and tempering as heat treatment, sothat the surface layer of the output shaft 2 has a surface hardness ofHRC57 to 62. The output shaft 2 may also be of a machined product of asteel material.

[0147]FIG. 4 shows the inner ring 3, which serves as a control member.The inner ring 3 comprises a cylindrical portion 3 a, a flange portion 3b extending radially outwards from one end of the cylindrical portion 3a, and a plurality of (eight in this embodiment) column portions 3 cextending from the peripheral edge of the flange portion 3 b axiallytoward one side. The cylindrical portion 3 a is mounted on the journalportion 2 a of the output shaft 2, while being inserted inside of theouter ring 1. An inner periphery of the cylindrical portion 3 a at theother end is formed with a radial bearing surface 3 a 1 for radiallysupporting the journal portion 2 a of the output shaft 2, while at theone end is formed with circumferential surface 3 a 2, which defineswedge gaps in both normal and reverse directions of rotational togetherwith the cam surfaces 1 d of the outer ring 1. The flange portion 3 b isformed with a plurality of (eight in this embodiment) pins 3 b 1 axiallyextending toward one side and circumferentially spaced at certainintervals. These pins 3 b 1 are respectively received in the pin holes 2b 3 of the output shaft 2. Between the circumferentially arrangedadjacent column portions 3 c are formed pockets 3 c 1 opened toward oneside of the axial direction, in which rollers 20 of the second clutchpart 6, to be described later with reference to FIG. 14, areaccommodated.

[0148] The inner ring 3 is, for example, is forged with a steel materialsuch as steels for case hardening, carbon steels for machine structuraluse, or bearing steels, and then undergoes suitable heat treatment suchas carburizing and tempering, carbonitriding and tempering with, inducedhardening and tempering, or dip quenching and tempering. In thisembodiment, steel for case hardening such as chromium-molybdenum steelSCM415 is employed for the inner ring 3, which is subjected tocarburizing and tempering as heat treatment, so that the surface layerof the inner ring 3 has a surface hardness of HRC57 to 62. The innerring 3 may also be of a machined product of a steel material, or apress-formed product of a steel plate such as a cold rolled steel sheet.

[0149]FIG. 5 shows the outer ring 4, which serves as a stationary-sidemember. The outer ring 4 comprises a radially extending flange portion 4a, engaged portions 4 b extending from the inner peripheral edge of theflange portion 4 a toward one side of the axial direction, a cylindricalportion 4 c extending from the outer peripheral edge of the flangeportion 4 a toward the other side of the axial direction, and an collarportion 4 d radially extending outwards from one end of the cylindricalportion 4 c. The flange portion 4 a is formed with a plurality of (threein this embodiment) stoppers 4 a 1 protruded toward one side of theaxial direction and arranged circumferentially at predeterminedintervals. The stoppers 4 a 1 make engagement with the protrusions 1 a 2of the outer ring 1 in the direction of rotation, thereby restrictingthe rotation range of the outer ring 1. The engaged portions 4 b arepaired and formed in an arc shape, for example. The engaged portions 4 bare mounted on the outer periphery of the cylindrical portion 3 a of theinner ring 3, while being inserted in the inner periphery of engagedportions 11 b of the retainer 11 (see FIG. 9) of the first clutch part5, to be described later. With both ends of one of the engaged portions4 b, a centering spring 12 (see FIG. 10) of the first clutch part 5engages.

[0150] An inner periphery of the cylindrical portion 4 c is formed withan inner circumferential surface defining wedge gaps together with thecam surfaces 2 b 1 of the output shaft 2 in both normal and reversedirections of rotational. The collar portion 4 d is formed with aplurality of (three in this embodiment) arc-shaped cutouts 4 d 1 and aplurality of (six in this embodiment) rectangular cutouts 4 d 2 atcircumferentially spaced intervals. The cutouts 4 d 1 match the shape ofcaulking members 8 (see FIG. 1) of a fixing side plate 7, which will bedescribed later. The cutouts 4 d 2 engage circumferentially withprojections 7 c of the fixings side plate 7 (see FIG. 6), therebypreventing rotation of the outer ring 4 relative to the fixing sideplate 7. Claws 7 d of the fixing side plate 7 are caulked to the collarportion 4 d.

[0151] The outer ring 4 is, for example, forged with a steel materialsuch as steels for case hardening, carbon steels for machine structuraluse, or bearing steels, and then undergoes suitable heat treatment suchas carburizing and tempering, carbonitriding and tempering, inducedhardening and tempering, or dip quenching and tempering. In thisembodiment, steel for case hardening such as chromium-molybdenum steelSCM415 is employed for the outer ring 4, which is subjected tocarburizing and tempering as heat treatment, so that the surface layerof the outer ring 4 has a surface hardness of HRC57 to 62. The outerring 4 may also be of a machined product of a steel material, or apress-formed product of a steel plate such as a cold rolled steel sheet.

[0152]FIG. 6 shows the fixing side plate 7, which is fixed to the outerring 4. The fixing side plate 7 comprises a radially extending flangeportion 7 a, a plurality of (three in this embodiment) bracket portions7 b radially protruding outwards from the outer peripheral end of theflange portion 7 a, a plurality of (six in this embodiment) projections7 c extending from the outer peripheral end of the flange portion 7 atoward one side in the axial direction, a plurality of (three in thisembodiment) claws 7 d, and an annular boss portion 7 e protruding fromthe inner peripheral end of the flange portion 7 a toward one side inthe axial direction. The three bracket portions 7 b arecircumferentially spaced at predetermined intervals, and each of themhas a through hole 7 b 1. The through holes 7 b 1 are provided forreceiving hollow caulking members 8 shown in FIG. 1. The caulking member8 may be integrally formed with the bracket portion 7 b. The sixprojections 7 c are arranged at spaced intervals in the circumferentialdirection, and they respectively engage in the direction of rotationalwith the cutouts 4 d 2 of the outer ring 4, thereby stopping the outerring 4 from rotating relative to the fixing side plate 7. The threeclaws 7 d are circumferentially arranged at predetermined intervals, andrespectively caulked to the collar portion 4 d of the outer ring 4, soas to prevent axial movement of the outer ring 4 relative to the fixingside plate 7.

[0153] The boss portion 7 e includes a plurality of (six in thisembodiment) projections 7 e 1 formed circumferentially around the outerperiphery thereof at spaced intervals, and a radial bearing surface 7 e2 formed on the inner periphery thereof. The boss portion 7 e isinserted into the annular recess 2 b 4 of the output shaft 2, and afriction member 9, which will be described later with reference to FIG.7, is fitted with interference in the gap between the outer periphery ofthe boss portion 7 e and the outer circumferential wall of the annularrecess 2 b 4. The projections 7 e 1 of the boss portion 7 e respectivelyengage with recesses 9 a of the friction member 9 in the direction ofrotational, so as to prevent the friction member 9 from rotatingrelative to the fixing side plate 7. The radial bearing surface 7 e 2 ofthe boss portion 7 e is mounted on the journal surface 2 b 5 of theannular recess 2 b 4, thereby radially supporting the journal surface 2b 5.

[0154] The fixing side plate 7 is a press-formed product of a steelplate such as a cold rolled steel sheet, for example SPCE, as in thispreferred embodiment. The fixing side plate 7 used in this embodimenthas not undergone any heat treatment in consideration of workabilitywhen caulking the claws 7 d. Alternatively, the fixing side plate 7 mayundergo carburizing (or carbonitriding), after subjecting the portionsto be caulked such as claws 7 d to anti-curburizing treatment (oranti-carbonitriding treatment).

[0155]FIG. 7 shows the friction member 9, which serves as a brake means.The friction member 9 in this embodiment is formed in a ring-like shapeand has a plurality of, for example six, recesses 9 a arrangedcircumferentially at predetermined intervals along the inner peripherythereof. The recesses 9 a engage with the projections 7 e 1 of the bossportion 7 e of the fixing side plate 7 in the direction of rotational,thereby preventing the friction member 9 from rotating relative to thefixing side plate 7.

[0156] The friction member 9 is made of elastic material such as rubberor synthetic resin, and press-fitted between the outer periphery of theboss portion 7 e of the fixing side plate 7 and the outercircumferential wall of the annular recess 2 b 4 of the output shaft 2.The friction generated between the outer periphery of the frictionmember 9 and the outer circumferential wall of the annular recess 2 b 4applies a braking force (frictional braking force) to the output shaft 2in the direction of rotational. The braking force (braking torque) maybe suitably set in accordance with the reverse input torque presumed tobe input from the output shaft 2. In order to effectively prevent theflow back phenomenon of the reverse input torque, the braking force(braking torque) should preferably be set substantially the same as thepresumed reverse input torque. In the case of the seat-height-adjustingdevice, the braking force (braking torque) should preferably be setsubstantially the same as the reverse input torque applied to the outputshaft 2 when a sitter is seated on the sitting seat. By using thefriction member 9 as brake means in this embodiment, the braking forceis advantageously, freely adjustable by changing the size of theinterference for the friction member 9.

[0157] The friction member 9 can be made of any materials. In thispreferred embodiment, the friction member 9 is of an injection-moldedproduct of synthetic resin composed of polyacetar (POM) and glass fiberof 30% in weight.

[0158]FIG. 8 is a cross-section taken along the line B-B of FIG. 1 andshows the first clutch part 5. The first clutch part 5 comprises aplurality of, for example ten, cam surfaces 1 d provided to the outerring 1, the circumferential surface 3 a 2 provided to the inner ring 3,a plurality of, for example ten, rollers 10 as engaging membersinterposed between the cam surfaces 1 d and the circumferential surface3 a 2, a retainer 11 for retaining the rollers 10, and an elasticmember, which is for example a centering spring 12 (see FIG. 10) as inthis embodiment, for coupling the retainer 11 with the outer ring 4 inthe direction of rotational. The cam surfaces 1 d, the circumferentialsurface 3 a 2, and the rollers 10 constitute locking means, while theretainer 11 and the centering spring 12 constitute returning means. Thecam surfaces 1 d defines wedge gaps in both normal and reversedirections of rotation together with the circumferential surface 3 a 2.An operation lever 13 is connected to the outer ring 1, for inputtinginput torques in normal or reverse directions to the outer ring 1. Thespace between the inner periphery of the outer ring 1 and the outerperiphery of the inner ring 3 (the cylindrical portion 3 a),particularly between the cam surfaces 1 d and the circumferentialsurface 3 a 2, is filled with grease. The grease may be of any type, butin an application of this clutch unit for a vehicle seat-adjustingdevice, it is preferable to use a grease containing, as a base oil, alithium-base, urea-base, benton-base, or natrium-base lubricating oil,or a lubricating oil containing no extreme pressure additives, the baseoil having viscosity ranging from 10 to 1000 cSt at 37.8° C. This isbecause the temperature inside of the vehicle compartment can be as highas 80° C. when parked for a long time on a hot summer day.

[0159]FIG. 9 shows the retainer 11. The retainer 11 comprises aplurality of, for example ten, window-like pockets 11 a, and a pair ofengaged portions 11 b formed in an arc shape, for example, extendingaxially toward one side from one end face. The engaged portions 11 b aremounted on the outer periphery of the engaged portions 4 b of the outerring 4. With the end faces of one of the engaged portions 11 b, engagingportions 12 a of the centering spring 12 (see FIG. 10) are engaged.

[0160] The retainer 11 can be made of any materials. In this preferredembodiment, the retainer 11 is of an injection-molded product ofsynthetic resin composed of polyamide 66 (PA66) and glass fiber of 30%in weight.

[0161]FIG. 10 shows the centering spring 12. The centering spring 12comprises a pair of engaging portions 12 a bent radially inwards andopposed each other at a circumferentially spaced interval. The centeringspring 12 is made of wire, such as piano wire (SWPB), as in thispreferred embodiment.

[0162] The pair of engaging portions 12 a are made engagement with theengaged portion 11 b of the retainer 11 and the engaged portion 4 b ofthe outer ring 4 while widening an interval between the pair of theengaging portions 12 a in circumferential directions form the naturalstate. At that time, the diameter of the centering spring 12 is somewhatdecreased. With the use of the centering spring 12, the retainer 11 andthe outer ring 4 are coupled together in the direction of rotation. Forexample, when the retainer 11 rotates clockwise with respect to theouter ring 4 in FIG. 10(c), one of the engaging portions 12 a engaged atthe clockwise direction (forward in the direction of rotational) ispushed forward by the engaged portion 11 b of the retainer 11 andelastically displaced toward the clockwise direction, while the otherengaging portion 12 a engaged at the counterclockwise direction(backward in the direction of rotating) is stopped by the engagedportion 4 b of the outer ring 4. Thereby, the centering spring 12deforms in a manner wherein the interval between the pair of engagingportions 12 a are widened, i.e., the diameter of the centering spring 12decreases, and an elastic force is accumulated in accordance with theamount of deformation of the spring. The centering spring 12 accumulatesan elastic force in a similar manner in reverse motions when theretainer 11 rotates counterclockwise in FIG. 10(c) relative to the outerring 4.

[0163] Next, the function of the first clutch part 5 will be describedwith reference to FIGS. 11 through 13. In these drawings, the centeringspring 12 and the outer ring 4 are conceptualized and only schematicallyshown. Illustration of the operation lever 13 is omitted.

[0164]FIG. 11 shows the neutral position of the first clutch part 5 (inthe state shown in FIG. 8). In this position, each of the rollers 10 islocated in the middle of the respective cam surface 1 d, and comes outfrom the wedge gap defined between the cam surface 1 d and thecircumferential surface 3 a 2 in both normal and reverse directions ofrotation. The diameter of the roller 10 is set somewhat smaller than thedistance between the center of the cam surface 1 d and thecircumferential surface 3 a 2 along the radial direction, so that thereis a clearance in the radial direction between the roller 10 and thecenter of the cam surface 1 d, and between the roller 10 and thecircumferential surface 3 a 2. A reverse input torque input from theoutput shaft 2 is locked in both forward and reverse directions ofrotation by the second clutch part 6, as will be described later.Therefore, the inner ring 3 rotates only in response to the input torqueinput from the operation lever 13 (the outer ring 1), and remains inposition even when a reverse input torque is input from the output shaft2.

[0165]FIG. 12 shows a state wherein an input torque has been input tothe outer ring 1 by a pivoting movement of the operation lever 13. Whenthe input torque in the counterclockwise direction, for example, inputto the outer ring 1, the cam surfaces 1 d relatively move in thecounterclockwise direction with respect to the rollers 10 accompany withthe rotation of the outer ring 1, thereby the rollers 10 come intowedging engagements with the wedge gaps. Thus, the input torque from theouter ring 1 is transmitted to the inner ring 3 through the rollers 10.As a result, the outer ring 1, the rollers 10, the retainer 11, and theinner ring 3 all rotate in the counterclockwise direction together. Therotation of the retainer 11 causes the centering spring 12 to deform,whereby an elastic force f in accordance with the amount of deformationis accumulated. The maximum range of the rotation amount of the outerring 1 is restricted by the engagements between the protrusions 1 a 2 ofthe outer ring 1 and the stoppers 4 a 1 of the outer ring 4.

[0166]FIG. 13 shows a state wherein the operation lever 13 (the outerring 1) has been released after the state shown in FIG. 12. The elasticforce f accumulated in the centering spring 12 applies the rotationaldriving force on the retainer 11 in the clockwise direction, whereby therollers 10 are pushed by the retainer 11 to press the cam surfaces 1 d.Thereupon, as the outer ring 1 has been released, the rollers 10, theretainer 11, and the outer ring 1 freewheel in the clockwise directionwith respect to the inner ring 3, thus returning to the neutral positionshown in FIG. 11. At this time, the inner ring 3 remains at the positiongiven by the rotating operation shown in FIG. 12. Accordingly, when therotating operation shown in FIG. 12 is repeated, the amount of rotationgiven by each of the rotating operations is accumulated insuperimposition to the inner ring 3. It should be noted that, if theinput torque is input to the outer ring 1 in FIG. 11 in clockwisedirection, the first clutch part 5 operates in reverse movements.

[0167]FIG. 14 is a cross-section taken along the line A-A of FIG. 1, andshows the second clutch part 6. The second clutch part 6 comprises thecircumferential surface 4 c 1 provided to the outer ring 4, theplurality of, for example eight, cam surfaces 2 b 1 provided to theoutput shaft 2, a plurality of, for example eight, pairs of rollers 20as engaging members interposed between each of the cam surfaces 2 b 1and the circumferential surface 4 c 1, a plurality of elastic members,such as plate springs 21 having a U-shaped cross-section, interposedbetween each pair of rollers 20, the column portions 3 c of the innerring 3, the pins 3 b 1 of the inner ring 3 and the pin holes 2 b 3 ofthe output shaft 2. The cam surface 2 b 1, the circumferential surface 4c 1, the paired rollers 20, and the plate spring 21 constitute each ofthe locking means, while the column portions 3 c of the inner ring 3positioned on both circumferential sides of the paired rollers 20constitute each of the lock releasing means. The pin 3 b 1 of the innerring 3 and the pin hole 2 b 3 of the output shaft 2 constitute each ofthe torque transmission means. In this embodiment, the plate springs 21are made of stainless steel, for example SUS301CPS-H, which hasundergone tempering as a heat treatment. The space between the innerperiphery of the outer ring 4 and the outer periphery of the outputshaft 2 (the large-diameter portion 2 a), particularly between the camsurfaces 2 b 1 and the circumferential surface 4 c 1, is filled withgrease. The grease may be of any type, but preferably it should contain,as a base oil, a lithium-base, urea-base, benton-base, or natrium-baselubricating oil, or a lubricating oil containing no extreme pressureadditives, the base oil having viscosity ranging from 10 to 1000 cSt at37.8° C. This is because the temperature inside of the vehiclecompartment can be as high as 80° C. when parked for a long time on ahot summer day.

[0168]FIG. 15 shows the second clutch part 6 to a larger scale, which islocated in a neutral position. In this position, the pairs of rollers 20are biased by the plate springs 21 toward the wedge gaps defined betweenthe cam surface 2 b 1 and the circumferential surface 4 c 1 in bothnormal and reverse directions of rotational. At this time, there is arotational direction clearance δ1 between each of the rollers 20 and theadjacent column portion 3 c of the inner ring 3. There is also arotational direction clearance 2 in normal and reverse directions ofrotational respectively between each of pins 3 b 1 of the inner ring 3and the pin holes 2 b 3 of the output shaft 2. The rotational directionclearance δ2 is larger than the rotational direction clearance δ1. Therotational direction clearance δ1 is about 0 to 0.4 mm, at an angle of 0to 1.5° with respect to the center axis of the second clutch part 6. Therotational direction clearance δ2 is about 0.4 to 0.8 mm, at an angle of1.8 to 3.7° with respect to the axis of the second clutch part 6.

[0169] In the state shown in FIG. 15, when a reverse input torque, forexample, in the clockwise direction is input to the output shaft 2, theroller 20 in the counterclockwise direction (backward in the directionof rotating) comes into wedging engagement with the wedge gap at thatdirection, thereby the output shaft 2 is locked clockwise with respectto the outer ring 4. When a reverse input torque in the counterclockwisedirection is input to the output shaft 2, the roller 20 in the clockwisedirection (backward in the direction of rotating) comes into wedgingengagement with the wedge gap at that direction, thereby the outputshaft 2 is locked counterclockwise with respect to the outer ring 4.Thus, the reverse input torque input from the output shaft 2 isprevented from being transmitted in both normal and reverse directionsof rotation by the second clutch part 6.

[0170]FIG. 16 shows an initial state where the input torque (clockwisein the diagram) from the outer ring 1 is input to the inner ring 3through the first clutch part 5 so that the inner ring 3 starts torotate clockwise in the diagram. Since the rotational directionclearances are set as δ1<δ2, the column portion 3 c of the inner ring 3in the counterclockwise direction (backward in the direction ofrotation) initially comes into wedging engagement with the roller 20 inthat direction (backward in the direction of rotation) and pushes itclockwise (forward in the direction of rotation) against the elasticforce of the plate spring 21. Thereby, the roller 20 in thecounterclockwise direction (backward in the direction of rotation) comesout from the wedge gap in that direction, so that the locked state ofthe output shaft 2 is releases. At this time, the roller 20 in theclockwise direction (forward in the direction rotation) does not comeinto wedging engagement with the wedge gap in that direction.Accordingly, the output shaft 2 becomes to be rotatable in the clockwisedirection.

[0171] When the inner ring 3 is further rotated clockwise the pins 3 b 1of the inner ring 3 come into engagement with the pin holes 2 b 3 of theoutput shaft 2, shown in FIG. 17 clockwise. Thereby, the input torque inthe clockwise direction from the inner ring 3 is transmitted to theoutput shaft 2 through the pins 3 b 1 and the pin holes 2 b 3, so thatthe output shaft 2 is rotated in the clockwise direction. When the inputtorque in the counterclockwise direction is input to the outer ring 1,the output shaft 2 is rotated counterclockwise in reverse motions asdescribed above. Thus, the input torque from the outer ring 1 in bothnormal and reverse directions of rotation are transmitted to the outputshaft 2 through the first clutch part 5, the inner ring 3, and the pins3 b 1 and the pin holes 2 b 3 as the torque transmission means, so thatthe output shaft 2 is rotated in both normal and reverse directions ofrotation. When the input of torque from the inner ring 3 is stopped, theelastic returning force of the plate springs 21 causes the second clutchpart 6 to return to the neutral position shown in FIG. 15.

[0172] The outer ring 1, the output shaft 2, the inner ring 3, the outerring 4, the first clutch part 5, the second clutch part 6, the fixingside plate 7, and the friction member 9 describe above are assembled asshown in FIG. 1 to complete the clutch unit of this embodiment. Theoperation lever 13 made of e.g. resin is connected to the outer ring 1,and the output shaft 2 is connected to a rotating member of anoutput-side mechanism (not shown). The fixing side plate 7 is fixed to afixing member such as a casing (not shown) by caulking the caulkingmembers 8. Incidentally, the outer ring 1 is restrained between a washer18 attached to outside the collar portion 1 c and the flange portion 4 aof the outer ring 4 so as not to come off from either of the axialsides.

[0173] In the first clutch part 5, the centering spring 12 isaccommodated in the inner periphery of the protrusions 1 a 2 of theouter ring 1, and restrained between one end face of the outer ring 1and the flange portion 4 a of the outer ring 4 so as not to come offfrom either of the axial sides. In addition, the retainer 11 and therollers 10 are restrained between the collar portion 1 c of the outerring 1 and the flange portion 4 a of the outer ring 4 so as not to comeoff from either of the axial sides. The retainer 11, the rollers 10, andthe centering spring 12 of the first clutch part 5 are accommodatedinside the outer ring 1 with no protrusion toward the input-sideportion. Moreover, the engaged portions 11 b of the retainer 11 aremounted on the outer periphery of the engaged portions 4 b of the outerring 4, so that the rotation of the retainer 11 is guided by the engagedportions 4 b of the outer ring 4. The retainer 11 thus can rotatewithout a tilt, ensuring smooth clutching operation.

[0174] The second clutch part 6 is compactly accommodated in a spacesurrounded by the outer ring 4 and the fixing side plate 7 in radial andaxial direction. Besides, the column portions 3 c serving as the lockreleasing means and the pins 3 b 1 serving as the torque transmittingmeans are integrally formed to the inner ring 3, with smaller partscount and simple structure.

[0175] Furthermore, because the output shaft 2 is supported in a stateof straddle with the radial bearing surface 3 a 1 of the inner ring 3and the radial bearing surface 7 e 2 of the fixing side plate 7, theoutput shaft 2 stabilizes in rotation, and the first clutch part 5 andthe second clutch part 6 are less prone to partial load, allowing smoothclutch operation.

[0176]FIG. 18 shows a seat 30 equipped in a compartment of a vehicle.The seat 30 is composed of a sitting seat 30 a and a backrest 30 b, andcomprises a seat-height-adjusting device 31 for adjusting the height Hof the sitting seat 30 a, a seat-inclination-adjusting device 32 foradjusting the inclination angle θ of the backrest 30 b, and aseat-slide-adjusting device (not shown) for adjusting the position L ofthe sitting seat 30 a in forward and backward directions. The adjustmentof height H of the sitting seat 30 a is effected through the operationlever 31 a of the seat-height-adjusting device 31. The adjustment of theinclination angle θ of the backrest 30 b is effected through theoperation lever 32 a of the seat-inclination-adjusting device 32. Theadjustment of the position L in forward and backward directions of thesitting seat 30 a is effected through an operation lever (not shown) ofthe seat-slide-adjusting device. The clutch unit of the embodimentdescribed above is incorporated in the seat-height-adjusting device 31,for example.

[0177]FIG. 19(a) is a schematic view showing one example of theseat-height-adjusting device 31. One end of a link member 31 c and oneend of a link member 31 d are pivotally connected to a slidable member31 b 1 of a seat slide adjuster 31 b respectively. The other ends of thelink members 31 c and 31 d are pivotally connected to the sitting seat30 a respectively. The other end of the link member 31 c is alsopivotally connected to a sector gear 31 f through a link member 31 e.The sector gear 31 f is pivotally connected to the sitting seat 30 a,and is able to pivot around a fulcrum 31 f 1. The clutch unit X of theembodiment described above is fixed to an appropriate region of thesitting seat 30 a through the fixing side plate 7. An operation lever 31a made of, e.g., resin (corresponding to the operation lever 13 in FIGS.1 and 8) is connected to the outer ring 1 thereof. A pinion gear 31 gfor meshing with the sector gear 31 f is connected to the output shaft2.

[0178] For example, in FIG. 19(b), when the operation lever 31 a isoperated to pivot in the counterclockwise direction (upward), an inputtorque in that direction is transmitted to the pinion gear 31 g throughthe clutch unit X so that the pinion gear 31 g rotates in thecounterclockwise direction. Then, the sector gear 31 f meshing with thepinion gear 31 g pivots clockwise to pull the other end of the linkmember 31 c through the link member 31 e. As a result, the link member31 c and the link member 31 d are both erected to elevate the sittingsurface of the sitting seat 30 a. After the height H of the sitting seat30 a is adjusted in this way, the operation lever 31 a is released.Because of the elastic force (elastic returning force) of the centeringspring 12 of the first clutch part 5, the operation lever 31 a pivotsclockwise to return to its original position (neutral position)Incidentally, when the operation lever 31 a is operated to pivot in theclockwise direction (downward), the sitting surface of the sitting seat31 a sinks by the action reverse to the foregoing. Moreover, when theoperation lever 31 a is released after the height adjustment, theoperation lever 31 a pivots in the counterclockwise direction to returnto its original position (neutral position).

[0179] According to the seat-height-adjusting device 31 described above,the height H of the sitting seat 30 a is adjustable only by the pivotingoperation of the operation lever 13. The height position of the sittingseat 30 a after the height adjustment is automatically maintained. Theoperation lever 13, when released, automatically returns itself smoothlyto its neutral position, without generating any noise as in a ratchetmechanism. Moreover, the braking force in the rotational direction isapplied to the output shaft 2 by the friction member 9, so that the flowback phenomenon of the reverse input torque when operating the lever 13is eliminated or reduced, ensuring stable adjusting operation.

[0180]FIG. 20 shows a clutch unit according to the second embodiment ofthe present invention. The clutch unit according to the embodiment isdifferent from the clutch unit according to the first embodimentdescribed above in that the friction member 9, as the braking means,made of an elastic material such as rubber or synthetic resin isreplaced with a friction member 15 having spring elasticity, as thebraking means. The friction member 15 is made of a metallic materialsuch as spring steel, and comprises a fitting portion 15 a fitted in theouter circumferential wall of the annular recess 2 b 4 of the outputshaft 2, a collar portion 15 b continuous with one end of the fittingportion 15 a, and a plurality of, for example eight, projections 15 cradially extending outwards from the collar portion 15 b. The fittingportion 15 a is press-fitted with interference to the outercircumferential wall of the annular recess 2 b 4 of the output shaft 2,thereby preventing the friction member 15 from rotating relative to theoutput shaft 2. Each of the projections 15 c includes a radiallyextending piece 15 c 1 and a tongue 15 c 2 obliquely extending from theend of the radially extending piece 15 c 1. The tongues 15 c 2 of thefriction member 15 fit to the inner periphery of the outer ring 4 withinterference, thereby providing a braking force (frictional brakingforce) to the output shaft 2 in the direction of rotation. The fittingportion 15 a of the friction member 15 may take any form as long as itis capable of preventing from the rotation relative to the outercircumferential wall of the annular recess 2 b 4. In addition to the fitwith interference as described above, it may make projection-recessengagement in the direction of rotation with the outer circumferentialwall of the annular recess 2 b 4, for example. Since other respects ofthe embodiment are identical or similar to the first embodimentdescribed above, the descriptions thereof are omitted.

[0181]FIG. 21 shows a clutch unit according to the third embodiment ofthe present invention. The clutch unit according to the embodiment isdifferent from the clutch unit according to the first embodimentdescribed above in that the friction member 9, as the braking means,made of an elastic material such as rubber or synthetic resin isreplaced with a friction member 16 having spring elasticity, as thebraking means. The friction member 16 is made of a metallic materialsuch as spring steel, and includes a mount portion 16 a mounted on theboss portion 7 e of the fixing side plate 7, a collar portion 16 bcontinuous with one end of the mount portion 16 a, and a plurality of,for example twelve, projections 16 c radially extending outwards fromthe collar portion 16 b. The mount portion 16 a includes a plurality of,for example twelve, cutouts 16 a 1, for engaging in the direction ofrotational with corresponding projections formed on the boss portion 7 eof the fixing side plate 7, so as to prevent rotation of the frictionmember 16 relative to the fixing side plate 7. Each of the projections16 c includes a curved part 16 c 1, and a tongue 16 c 2 obliquelyextending from the end of the curved part 16 c 1. The tongues 16 c 2 ofthe friction member 16 fit to the outer circumferential wall of theannular recess 2 b 4 of the output shaft 2 with interference, therebyproviding a braking force (frictional braking force) to the output shaft2 in the rotational direction. The mount portion 16 a of the frictionmember 16 may take any form as long as it is capable of preventing fromthe rotation relative to the boss portion 7 e of the fixing side plate7. In addition to the projection-recess engagement in the direction ofrotation as described above, it may make fit with interference to theboss portion 7 e of the fixing side plate 7, for example. Since otherrespects of the embodiment are identical or similar to the firstembodiment described above, the descriptions thereof are omitted.

[0182]FIG. 22 shows the entire structure of a clutch unit according to afourth embodiment of the present invention. The clutch unit of thisembodiment comprises an outer ring 1 as an input-side member, an outputshaft 2 as an output-side member, an inner ring 3 as a control member,an outer ring 4 as a stationary-side member, a first clutch part 5arranged between the outer ring 1 and the inner ring 3, and a secondclutch part 6 arranged between the outer ring 4 and the output shaft 2.

[0183]FIG. 23 shows the outer ring 1, as the input-side member. Aplurality (three, for example) of ribs 1 a, a plurality (four, forexample) of ribs 1 b, a plurality (two, for example) of ribs 1 e, andone or more ribs 1 f protruding outward are formed on the outerperiphery of the outer ring 1 at predetermined circumferentialintervals. An axial end portion of each rib 1 a axially protrudes froman end of the outer ring 1, thereby forming a protruding portion 1 a 2.In addition, the outer periphery of any one of the three ribs 1 a, forexample, the rib 1 a lying at the top in the diagram is provided with adistinction mark 1 a 1 intended for directional distinction in mountingthis clutch unit on a mating member. In this embodiment, the distinctionmark 1 a 1 has the shape of an axial groove. These ribs 1 a, 1 b, 1 e,and 1 f are engaged, in the direction of rotation, with the operationlever (13: see FIGS. 29 and 30) to be mounted on the outer periphery ofthe outer ring 1, thereby preventing the operation lever (13) fromrelative rotation with respect to the outer ring 1.

[0184] Axial screw holes 1 b 1 are formed in the ribs 1 b. Axialrelative movement of the operation lever (13) with respect to the outerring 1 is prevented by screwing the operation lever (13) to the screwholes 1 b 1 in the ribs 1 b. As shown in FIG. 30, in this embodiment,the outer ring 1 is shaped horizontally symmetric with respect to the Yaxis in the diagram so that the operation lever (13) can be connectedthereto either of rightward or leftward, whereby the clutch unit and theoperation level (13) may be arranged on either of right and left sidesof a seat depending on whether the vehicle is of right-hand drive orleft-hand drive, and such factors as car-body and seat design. In thiscase, the operating torque of the operation lever (13) acts chiefly onthe screwing portions of two ribs 1 b lying at 180° opposite positions.Thus, these two ribs 1 b may be provide with the screw holes 1 b 1 whileprepared holes (through holes) for machining screw holes 1 b 1 are leftas-is in the other two ribs 1 b. This allows a reduction in themachining cost for hole threading. For example, when the operation lever(13) is connected rightward in the diagram (full line), the two ribs 1 blying on the oblique line that is inclined rightward with respect to theY axis in the diagram are provided with the screw holes 1 b 1 while thetwo ribs 1 b lying on the oblique line inclined leftward are given theprepared holes 1 b 1′. The arrangement shall be inverted from theforegoing when the operation lever (13) is connected rightward in thediagram (double-dotted chain line). Needless to say, the screw holes 1 b1 may be formed in all the four ribs 1 b.

[0185] The inner periphery of the protruding portions 1 a 2 accommodatesa centering spring (12: see FIG. 32) of the first clutch part (5) to bedescribed later. Besides, the protruding portions 1 a 2 are engaged withstopper portions (4 a 1) of the outer ring (4: see FIG. 26) to bedescribed later, in the direction of rotation, so that the outer ring 1is restrained in the range of rotation.

[0186] A collar portion 1 c extending inward is formed on the innerperiphery of the outer ring 1 at the other end. This collar portion 1 chas the functions of restraining a retainer (11: see FIGS. 22 and 31) ofthe first clutch part (5) to be described later from coming off in oneof the axial directions, and maintaining the outer ring 1 coaxial to theinner ring 3. Moreover, a plurality (ten, for example) of cam surfaces 1d are formed on the inner periphery of the outer ring 1 atcircumferential regular intervals. Each cam surface 1 d is deep in itscircumferential center, and gets shallower obliquely toward bothcircumferential sides.

[0187] The outer ring 1 is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the outer ring 1).

[0188]FIG. 24 shows the output shaft 2, as the output-side member. Theoutput shaft 2 has a journal portion 2 a on one end, a large-diameterportion 2 b at the center, and a connecting portion 2 c on the otherend. The journal portion 2 a is inserted in a radial bearing surface (3a 1) of the inner ring (3: see FIG. 25) to be described later. Aplurality (eight, for example) of cam surfaces 2 b 1 are formed on theouter periphery of the large-diameter portion 2 b at circumferentialregular intervals. Each cam surface 2 b 1 is formed into a flat surfacethat makes a chord of a circle around the axial center of the outputshaft 2. A plurality (eight, for example) of pin holes 2 b 3 are formedin one side of the large-diameter portion 2 b at circumferential regularintervals. Pins (3 b 1) of the inner ring (3: see FIG. 25) to bedescribed later are inserted in these pin holes 2 b 3. Besides, anannular recess 2 b 4 is formed in the other side of the large-diameterportion 2 b. A frictional member (9: see FIG. 28) to be described lateris attached to this annular recess 2 b 4. Moreover, the inner peripheralwall 2 b 5 of the annular recess 2 b 4 makes a journal surface to beinserted in a radial bearing surface (7 e 2) of the fixing side plate(7: see FIG. 27) to be described later. The connecting portion 2 c isprovided with a tooth profile 2 c 1 intended for connecting to anotherrotating member.

[0189] The output shaft 2 is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the output shaft 2).

[0190]FIG. 25 shows the inner ring 3, as the control member. The innerring 3 comprises a cylindrical portion 3 a, a flange portion 3 bextending outward from one end of the cylindrical portion 3 a, and aplurality (eight, for example) of column portions 3 c extending in oneof the axial directions from the outer end of the flange portion 3 b.The cylindrical portion 3 a is mounted on the journal portion 2 a of theoutput shaft 2, and inserted into the outer ring 1. A radial bearingsurface 3 a 1 for supporting the journal portion 2 a of the output shaft2 radially is formed on the inner periphery of the cylindrical portion 3a at the other end. A circumferential surface 3 a 2 for defining wedgegaps together with the cam surfaces 1 d of the outer ring 1 in both thenormal and reverse directions of rotation is formed on the outerperiphery of the cylindrical portion 3 a at the other end. The plurality(eight, for example) of pins 3 b 1 protruding in an axial direction areformed on the flange portion 3 b at circumferential regular intervals.These pins 3 b 1 are inserted in the pin holes 2 b 3 of the output shaft2, respectively. Pockets 3 c 1 opening to an axial direction are formedbetween the column portions 3 c adjoining circumferentially. Thesepockets 3 c 1 accommodate rollers (20) and plate springs (21) of thesecond clutch part (6: see FIG. 33) to be described later. Since therollers (20) and the plate springs (21) can be loaded into the pockets 3c 1 from the axial openings of the pockets 3 c 1, they are easy toassemble.

[0191] The inner ring 3 is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the inner ring 3).

[0192]FIG. 26 shows the outer ring 4, as the stationary-side member. Theouter ring 4 comprises a flange portion 4 a extending radially, acylindrical portion 4 c extending in one of the axial directions fromthe outer end of the flange portion 4 a, and a collar portion 4 dprotruding outward from an end of the cylindrical portion 4 c. Aplurality (three, for example) of stopper portions 4 a 1 protruding inthe other axial direction are formed on the flange portion 4 a asarranged at predetermined circumferential intervals. These stopperportions 4 a 1 are engaged with the protruding portions 1 a 2 of theouter ring 1 in the direction of rotation to restrain the range ofrotation of the outer ring 1. In addition, a pair of engaged portions 4a 2 protruding in the other axial direction and a plurality (two, forexample) of mounting portions 4 a 3 are formed on the flange portion 4a. Engaging portions (12 a 1, 12 a 2) of the centering spring (12: seeFIG. 32) of the first clutch part (5) to be described later are engagedwith the circumferentially external surfaces of the pair of engagedportions 4 a 2, respectively. Besides, a winding portion (12 a) of thecentering spring (12) is mounted on the outer periphery of the mountingportions 4 a 3.

[0193] A circumferential surface 4 c 1 for defining wedge gaps togetherwith the cam surfaces 2 b 1 of the output shaft 2 in both the normal andreverse directions of rotation is formed on the inner periphery of thecylindrical portion 4 c. A plurality (six, for example) of notches 4 d 1are formed in the collar portion 4 d at predetermined circumferentialintervals. The notches 4 d 1 match with caulking portions (7 c: see FIG.27) of the fixing side plate (7) to be described later.

[0194] The outer ring 4 is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the outer ring 4).

[0195]FIG. 27 shows the fixing side plate 7 to be fixed to the outerring 4. The fixing side plate 7 comprises a flange portion 7 a extendingradially, a plurality (four, for example) of bracket portions 7 bprotruding outward from the outer end of the flange portion 7 a, aplurality (six, for example) of caulking portions 7 c protruding in anaxial direction from the outer end of the flange portion 7 a, aplurality (four, for example) of engaged portions 7 a 1 protruding in anaxial direction from the flange portion 7 a, and a boss portion 7 eprotruding in an axial direction from the inner end of the flangeportion 7 a. The four bracket portions 7 b are formed at predeterminedcircumferential intervals, each having a caulking portion 7 b 1 of ahollow pin shape formed integrally (or separately). The six caulkingportions 7 c are formed at predetermined circumferential intervals, eachhaving a pair of tabs 7 c 1 branching in two. When these caulkingportions 7 c are attached to the notches 4 d 2 of the outer ring 4 withthe pairs of tabs 7 c 1 caulked into contact with the collar portion 4 din circumferential opposite directions, the outer ring 4 can beprevented from axial relative movement and rotational relative movementwith respect to the fixing side plate 7. The caulking portions 7 b 1 arefixed to the mounting holes of a mating member by caulking.

[0196] A radial bearing surface 7 e 2 is formed on the inner peripheryof the boss portion 7 e. The boss portion 7 e is inserted in the annularrecess 2 b 4 of the output shaft 2. The frictional member (9: see FIG.28) to be described later is attached to between the outer periphery ofthe boss portion 7 e and the outer peripheral wall of the annular groove2 b 4. The engaged portions 7 a 1 are engaged with recesses (9 a) of thefrictional member (9) in the direction of rotation, thereby preventingthe relative rotation of the frictional member (9) with respect to thefixing side plate 7. The radial bearing surface 7 e 2 of the bossportion 7 e is mounted on the journal surface 2 b 5 of the annularrecess 2 b 4 to support the journal surface 2 b 5 radially.

[0197] The fixing side plate 7 is formed, for example, by pressing asteel plate such as a cold-rolled steel sheet. In this embodiment, acold-rolled steel sheet (such as SPCE) is used as the steel plate forforming the fixing side plate 7. With consideration given to workabilityand the like during caulking, the caulking portions 7 c and 7 b 1 aregiven no heat treatment. Incidentally, the portions to be caulked, suchas the caulking portions 7 c and 7 b 1, may be given anti-carburizingprocessing (or anti-carbonitriding processing) before carburizing andtempering (or carbonitriding and tempering).

[0198]FIG. 40 shows the state where the outer ring 4 as thestationary-side member and the fixing side plate 7 are fixed bycaulking. As shown in FIGS. 40(a) and 40(c), the base parts of thecaulking portions 7 c formed on the fixing side plate 7 are engaged withthe notches 4 d 1 in the outer ring 4 where the pairs of tabs 7 c 1formed at the extremities of the caulking portions 7 c are bent incircumferentially opposite directions into contact with the collarportion 4 d of the outer ring 4 for caulking. This precludes the axialrelative movement and circumferential relative movement of the outerring 4 with respect to the fixing side plate 7.

[0199] Under this state, as shown in FIG. 40(b), the outer surface ofthe outer ring 4 (collar portion 4 d) and the outer surface of thefixing side plate 7 (caulking portions 7 c) are generally flush witheach other. When these members 4 and 7 are in this fixed state, there isno radial protrusion across the entire circumference. In addition, sincethe caulking portions 7 c protrude forward from the fixing side plate 7(leftward in FIG. 40(a)), no unnecessary protrusion lies on the backsideof the fixing side plate 7. As a result, the clutch unit can be mountedon a mating member smoothly without trouble.

[0200] Consequently, bending the caulking portions 7 c (the pairs oftabs 7 c 1) in the circumferential directions of the outer ring 4 causesno radial stress on the outer ring 4, thus precluding deformation in theradial directions of the outer ring 4. It is therefore possible to avoidcaulking-based imperfection in the roundness of the inner periphery ofthe outer ring 4, and maintain the normal clutching facility of thesecond clutch part 6. Moreover, since the pairs of tabs 7 c 1 are bentwith the caulking portions 7 c engaged with the notches 4 d 1, both theaxial movement and circumferential movement of the outer ring 4 withrespect to the fixing side plate 7 can be restrained only by bendingthese tabs 7 c 1. This ensures the fixed state, and achievessimplification of the work and improved efficiency of the work.

[0201]FIG. 41 shows another example of the state where the outer ring 4as the stationary-side member and the fixing side plate 7 are fixed bycaulking. As shown in FIGS. 41(a) and 41(c), caulking portions 7 cxformed to protrude outward from the outer end of the fixing side plate 7are bent inward so as to sandwich the outer end of the collar portion 4d of the outer ring 4 for caulking. In this case, the caulking portions7 cx are in contact with the outer surface and front surface of thecollar portion 4. This precludes the axial relative movement of theouter ring 4 with respect to the fixing side plate 7. Then, although notshown in the diagram, either the outer end of the collar portion 4 d ofthe outer ring 4 or the outer end of the fixing side plate 7 is providedwith a notch, and the other a protrusion. These notch and protrusion areengaged with each other to preclude the circumferential relativemovement of the ring 4 with respect to the fixing side plate 7.Incidentally, in this embodiment, the caulking portions 7 cx protrudeoutward from the outer end of the fixing side plate 7 by their thicknessas shown in FIG. 41(b). Nevertheless, notches may be formed in the outerend of the collar portion 4 d of the outer ring 4. In this structure,the caulking portions 7 cx are engaged with the notches so that thecaulking portions 7 cx do not protrude outward from the fixing sideplate 7.

[0202]FIG. 28 shows the frictional member 9 as braking means. In thisembodiment, the frictional member 9 has the shape of a ring, having aplurality (four, for example) of recesses 9 a formed in one of its endfaces at predetermined circumferential intervals. The recesses 9 a areengaged with the engaged portions 7 a 1 of the fixing side plate 7 inthe direction of rotation, thereby preventing the relative rotation ofthe frictional member 9 with respect to the fixing side plate 7.

[0203] The frictional member 9 is made of elastic-material such asrubber and synthetic resin, and is fit to the outer peripheral wall ofthe annular recess 2 b 4 of the output shaft 2 with interference, forexample. The frictional force occurring between the outer periphery ofthe frictional member 9 and the outer peripheral wall of the annularrecess 2 b 4 gives the output shaft 2 a braking force (frictionalbraking force) in the direction of rotation. The setting of the brakingforce (braking torque) from the frictional member 9 and the material forforming the frictional member 9 are in conformity with the firstembodiment.

[0204]FIG. 29 (B-B section of FIG. 22) shows the first clutch part 5.The first clutch part 5 comprises the plurality (ten, for example) ofcam surfaces 1 d provided to the outer ring 1, the circumferentialsurface 3 a 2 provided to the inner ring 3, a plurality (nine, forexample) of rollers 10 as engaging members interposed between the camsurfaces 1 d and the circumferential surface 3 a 2, the retainer 11 forretaining the rollers 10, and an elastic member for coupling theretainer 11 to the outer ring (4) in the direction of rotation, such asthe centering spring (12: see FIG. 32). The cam surfaces 1 d, thecircumferential surface 3 a 2, and the rollers 10 constitute lockingmeans. The retainer 11 and the centering spring (12) constitutereturning means. In this embodiment, the cam surfaces 1 d define wedgegaps together with the circumferential surface 3 a 2 in both the normaland reverse directions of rotation. Besides, the operation lever 13 isconnected to the outer ring 1. Input torque in the normal direction orreverse direction is input to the outer ring 1 from the operation lever13. Moreover, grease is filled into the space between the innerperiphery of the outer ring 1 and the outer periphery of the inner ring3 (cylindrical portion 3 a), especially between the cam surfaces 1 d andthe circumferential surface 3 a 2.

[0205]FIG. 31 shows the retainer 11. The retainer 11 comprises aplurality (ten, for example) of window-like pockets 11 a foraccommodating the rollers 10, and an engaged portion 11 b protruding inan axial direction from one of the end faces. The engaged portion 11 bis an arc-shaped protrusion to be inserted in the inner peripheral sideof the engaged portions 4 a 2 of the outer ring 4 as shown in FIG.32(c). In the present embodiment, axial notches 11 d 1 and 11 d 2 areformed in circumferential two positions of one end face 11 c of theretainer 11 (the end face opposed to the outer ring 4) to form theengaged portion 11 b. Both the circumferential sides 11 b 1 and 11 b 2of the engaged portion 11 b make portions to be engaged portions withwhich the engaging portions (12 a 1, 12 a 2) of the centering spring(12: see FIG. 32) engage. As shown in FIGS. 42(a) and 42(b), theperipheral regions of the pockets 11 a of the retainer 11 are providedwith roller stoppers 11 e at inner portions and outer portions opposedto the outer peripheries of the rollers 10. This can prevent the rollers10 from coming off the pockets 11 a during assembly, thereby improvingthe assemblability.

[0206] The material of the retainer 11 is in conformity with the firstembodiment.

[0207]FIG. 32 shows the centering spring 12. The centering spring 12 isa torsion coil spring having a plurality of turns (in the shown example,approximately three turns). Engaging portions 12 a 1 and 12 a 2 bentinward are formed on both ends of the turns of winding portion 12 a.This pair of engaging portions 12 a 1 and 12 a 2 are opposed to eachother at a predetermined circumferential spacing. In addition, theengaging portions 12 a 1 and 12 a 2 differ from each other in axialposition. When installed into the retainer 11, one engaging portion 12 a1 lies on the side of one end face 11 c of the retainer 11, and theother engaging portion 12 a 2 lies closer to the axial center. Thecentering spring 12 is made of a wire rod shaped noncircular, such asrectangular, in section. In this embodiment, a piano wire rod (SWPB) isused as the wire rod. Moreover, this centering spring 12 is a spring ofunwinding type to be unwound in use from its natural state, as well as aso-called pitched spring which is wound with spacings S between theturns of the winding portion 12 a as shown in FIG. 32(e). Such provisionof spacings S between the turns of the winding portion 12 a avoidsfrictional loss resulting from contact between the turns.

[0208] As shown in FIG. 32(b), when the centering spring 12 is in itsnatural state, the centers of the plurality of turns are offset to adirection opposite from the direction of shift of the individual windingcenters under unwinding deformation. In other words, the individualwinding centers of the winding portion 12 a of the centering spring 12are offset to a direction opposite from the direction in which theindividual winding centers shift when the angle of relative rotation ofthe retainer 11 with respect to the outer ring 4 increases in anassembled state to be described later. Then, when this centering spring12 is assembled with the first clutch part 5, the pair of engagingportions 12 a 1 and 12 a 1 are engaged with the engaged portion 11 b ofthe retainer 11 and the engaged portions 4 a 2 of the outer ring 4 withthe interval between the pair of engaging portions 12 a 1 and 12 a 2widened circumferentially (here, the centering spring 12 is unwound witha slight increase in diameter) as shown in FIG. 32(c). Consequently, theretainer 11 is coupled with the outer ring 4 in the direction ofrotation through the intervention of the centering spring 12. At thispoint, the individual winding centers of the centering spring 12 fall onthe same axis.

[0209] As shown in FIG. 32(d), when the retainer 11 is relativelyrotated clockwise with respect to the outer ring 4 from such a state,the engaging portion 12 a 1 of the centering spring 12 in the clockwisedirection (forward in the direction of rotation) is pressed by theengaged portion 11 b of the retainer 11 to make clockwise elasticdisplacement. At this point, the engaging portion 12 a 2 of thecentering spring 12 in the counterclockwise direction (backward in thedirection of rotation) is locked by the engaged portion 4 a 2 of theouter ring 4. Consequently, the centering spring 12 bends to thedirection in which the interval between the pair of engaging portions 12a 1 and 12 a 2 is widened, accumulating elastic force corresponding tothe amount of bending. In this case, the individual winding centers ofthe centering spring 12 shift as the increasing angle of relativerotation of the retainer 11. Since the individual winding centers fallon the same axis when the retainer 11 is not rotated relatively, theamounts of shift of the individual winding centers are small when theretainer 11 is relatively rotated by a predetermined angle.Subsequently, when the rotating force acting on the retainer 11 isreleased, the elastic force of the centering spring 12 centers theretainer 11 (engaged portion 11 b) to the neutral position shown in FIG.32(c). Incidentally, when the retainer 11 is relatively rotatedcounterclockwise from the state shown in FIG. 32(c), the engagingportion 12 a 2 of the centering spring 12 in the counterclockwisedirection is pressed by the engaged portion 11 b of the retainer 11 withcounterclockwise elastic displacement. The centering spring 12accumulates elastic force by the action reverse to the foregoing.

[0210] As above, since the individual winding centers of the centeringspring 12 make smaller amounts of shift when the retainer 11 is rotatedrelatively, there occurs no interference with the protruding portions 1a 2 of the outer ring 1 as the input-side member. As a result, theclutch unit that incorporates the first clutch part 5 having theabove-described centering spring 12 enhances in design flexibility, andthe clutch unit can be made smaller.

[0211] Incidentally, the foregoing structure of the centering spring 12is also applicable to a spring of winding type. That is, in the naturalstate shown in FIG. 39(a) described previously, the individual windingcenters of the winding type centering spring Ya shall be offset in adirection opposite to the direction in which the individual windingcenters shift as the increasing angle of relative rotation of theretainer in an assembled state. Then, the individual winding centers ofthe centering spring Ya are positioned on the same axis when theretainer (engaged portion Yb) is not rotated relatively in the assembledstate shown in FIG. 39(b) described previously. In this case, the innerdiameter of the centering spring Ya must be designed to a dimension notto cause interference with the retainer due to a reduction in diameter.

[0212] As above, with the normal and reverse rotations of the retainer11, the engaged portions 11 b 1 and 11 b 2 of the retainer 11 undergocircumferential pressing forces from the engaging portions 12 a 1 and 12a 2 due to elastic deformation of the centering spring 12. Here, sincethe engaged portions 11 b 1 and 11 b 2 of the retainer 11 protrudeaxially, the base parts of the engaged portions 11 b 1 and 11 b 2undergo circumferential moment, which might cause a crack or the likebetween the base parts and the pockets 11 a. To avoid this, the baseparts of the engaged portions 11 b 1 and 11 b 2 are desirably increasedin axial thickness by some means.

[0213] FIGS. 43(a) and 43(b) show a concrete example of the thickeningmeans. In FIG. 43(a), one notch 11 d 1 is made smaller in depth (in theaxial direction) than the other notch 11 d 2. That is, the bottom A ofthe notch 11 d 1 is located closer to the retainer end face 1 c than thebottom B of the other notch 11 d 2 is, so that the base part of theengaged portion 11 b 1 is thickened for improved durability of theretainer 11 (the double-dashed chain line shows the case where a notchhaving the same depth as that of the other notch 11 d 2 is formed). Theengaged portion 11 b 1 thickened at the base part by such means isengaged with the engaging portion 12 a 1 that lies closer to theretainer end face 11 c after assembly out of the engaging portions 12 a1 and 12 a 2 of the centering spring 12.

[0214] Meanwhile, the other engaging portion 12 a 2 lies closer to theaxial center of the retainer 11 after assembly than the engaging portion12 a 1 does. Thus, if the notch depth is made smaller as describedabove, sure engagement with the engaging portion 12 a 2 cannot beestablished. FIG. 43(b) shows the thickening means for such an engagedportion 12 a 2. A pocket near the base part of the engaging portion 12 a2 is formed as a small pocket 11 a′ having a smaller axial dimension. Inthis case, the distance between a pocket surface 11 a′1 of the smallpocket 11 a′ on the side of the retainer base surface 11 c and thebottom B of the notch 11 d 2 also becomes greater than the distancebetween the corresponding pocket surface 11 a 1 of another pocket 11 aand the bottom B of the notch 11 d 2, successfully thickening the basepart of the engaged portion 11 b 2. The small pocket 11 a′ is alsobeneficial in avoiding shrinkage during the injection molding of theresin retainer 11. When shrinkage does not matter, the small pocket 11a′ may be omitted for a holeless structure with the same effect.Incidentally, when the small pocket 11 a′ is provide, the small pocket11 a′ accommodates none of the rollers 10 as the engaging members.

[0215] Since the operation of the first clutch part 5 is the same as inthe first embodiment, description thereof will be omitted.

[0216]FIG. 33 (A-A section of FIG. 22) shows the second clutch part 6.The second clutch part 6 comprises the circumferential surface 4 c 1provided to the outer ring 4, the plurality (eight, for example) of camsurfaces 2 b 1 provided to the output shaft 2, a pair (a total of eightpairs, for example) of rollers 20 as engaging members interposed betweeneach of the cam surfaces 2 b 1 and the circumferential surface 4 c 1, anelastic member interposed between the pair of rollers 20, such as theplate spring 21, the column portions 3 c of the inner ring 3, the pins 3b 1 of the inner ring 3, and the pin holes 2 b 3 of the output shaft 2.The cam surfaces 2 b 1, the circumferential surface 4 c 1, the pair ofrollers 20, and the plate spring 21 constitute locking means. The columnportions 3 c of the inner ring 3 lying on both circumferential sides ofthe pair of rollers 20 constitute lock releasing means. The pins 3 b 1of the inner ring 3 and the pin holes 2 b 3 of the output shaft 2constitute torque transmitting means. Incidentally, in this embodiment,the plate springs 21 are made of stainless steel (SUS 301 CPS-H, forexample) and given tempering as heat treatment. Moreover, grease isfilled into the space between the inner periphery of the outer ring 4and the outer periphery of the output shaft 2 (large-diameter portion 2b), especially between the cam surfaces 2 b 1 and the circumferentialsurface 4 c 1.

[0217] In this embodiment, as shown in FIG. 44, the plate spring 21 isgenerally N-shaped in section, consisting of two arc-shaped bendingportions 21 a, a coupling portion 21 b for coupling the opposing ends ofthe bending portions 21 a to each other, and side plate portions 21 cextending from the other ends of both the bending portions 21 a. Theside plate portions 21 c are generally parallel flat surfaces, and thecoupling portion 21 b is shaped into a flat surface oblique thereto. Theplate spring 21 is made of stainless steel (SUS 301 CPS-H, for example),and further given tempering as heat treatment.

[0218] As shown enlarged in FIG. 34, in the neutral position, the pairof rollers 20 are pressed by the plate spring 21 toward the wedge gapsdefined between the cam surface 3 b 1 and the circumferential surface 4c 1 in both the normal and reverse directions of rotation, respectively.Here, the column portions 3 c of the inner ring 3 and the rollers 20have rotational direction clearances δ1 therebetween. Moreover, the pins3 b 1 of the inner ring 3 and the pin holes 2 b 3 of the output shaft 2have rotational direction clearances δ2 therebetween in both the normaland reverse directions of rotation. The rotational direction clearance61 and the rotational direction clearance δ2 have the relationship ofδ1<δ2. The magnitude of the rotational direction clearance δ1 is on theorder of 0 to 0.4 mm (0 to 1.5° about the axis of the second clutch part6), for example. The magnitude of the rotational direction clearance δ2is on the order of 0.4 to 0.8 mm (1.8 to 3.7° about the axis of thesecond clutch part 6), for example.

[0219] In the state shown in the diagram, for example, when clockwisereverse input torque is input to the output shaft 2, the roller 20 inthe counterclockwise direction (backward in the direction of rotation)makes wedge engagement with the wedge gap in that direction, whereby theoutput shaft 2 is locked clockwise with respect to the outer ring 4.When counterclockwise reverse input torque is input to the output shaft2, the roller 20 in the clockwise direction (backward in the directionof rotation) makes wedge engagement with the wedge gap in thatdirection, whereby the output shaft 2 is locked counterclockwise withrespect to the outer ring 4. Consequently, reverse input torques fromthe output shaft 2 are locked by the second clutch part 6 in both thenormal and reverse directions of rotation.

[0220]FIG. 35 shows an initial state where input torque (clockwise inthe diagram) from the outer ring 1 is input to the inner ring 3 throughthe first clutch part 5 so that the inner ring 3 starts to rotateclockwise in the diagram. Since the rotational direction clearances areset as δ1<δ2, the column portion 3 c of the inner ring 3 in thecounterclockwise direction (backward in the direction of rotation)initially comes into engagement with the roller in that direction(backward in the direction of rotation), and presses it clockwise(forward in the direction of rotation) against the elastic force of theplate spring 21. Consequently, the roller 20 in the counterclockwisedirection (backward in the direction of rotation) comes out from thewedge gap in that direction, releasing the locked state of the outputshaft 2. The output shaft 2 thus becomes capable of clockwise rotation.

[0221] When the inner ring 3 is further rotated clockwise, the pins 3 b1 of the inner ring 3 come into engagement with the pin holes 2 b 3 ofthe output shaft 2 clockwise. Consequently, the clockwise input torquefrom the inner ring 3 is transmitted to the output shaft 2 through thepins 3 b 1 and the pin holes 2 b 3, so that the output shaft 2 rotatesclockwise. When counterclockwise input torque is input to the outer ring1, the output shaft 2 rotates counterclockwise by the action reverse tothe foregoing. Thus, the input torques from the outer ring 1 in both thenormal and reverse directions of rotation are transmitted to the outputshaft 2 through the first clutch part 5, the inner ring 3, and the pins3 b 1 and the pin holes 2 b 3 as the torque transmitting means, so thatthe output shaft 2 rotates in both the normal and reverse directions ofrotation. Incidentally, when the input torque from the inner ring 3disappears, the elastic returning force of the plate spring 21 restoresthe neutral position shown in FIG. 34.

[0222] The pair of rollers 20 are pressed by the inner ring 3 each timethe locked state is released. Since the pressing narrows the gap (springspace) between the rollers 20, the plate spring 21 between the rollers20 undergoes large bending (stress). For that reason, the plate spring20 desirably has high elastic limit so as not to cause plasticdeformation even under such stress. The N-sectioned plate spring 21described above has two bending portions 21 a and thus bends smaller atthe bending portions 21 a, being less prone to plastic deformation ascompared to plate springs having a single bending portion alone, such asU-sectioned and V-sectioned ones. Thus, the use of the N-shaped platespring 21 allows a reduction in the dimension of the gap (spring space)between the rollers 20 for the miniaturization of the clutch unit.Moreover, in the cases of U-shaped and V-shaped plate springs, the camsurface 2 b 1 of the output shaft 2 requires an axial groove intended tomount the plate spring. Since the N-shaped plate spring 21 isfreestanding, grooves of this type are unnecessary. The cam surface 2 b1 may be a groove-free flat surface over a region for the plate springs21 to be mounted on. It is therefore possible to reduce the machiningcost of the output shaft 2 and avoid the problem of stress concentrationresulting from groove formation.

[0223] The plate spring 21 may have three or more bending portions 21 a.In that case, however, there is a fear that a sufficient pressing forcebecomes difficult to obtain and the spring space increases in size.Instead of the plate spring 21, a coil spring such as a conical springcan be used to obtain a sufficient elastic limit with a reduction in thesize of the spring space. Nevertheless, easy entanglement and hardseparation can cause a problem in terms of parts management. From theforegoing reasons, the plate spring 21, especially a plate spring havingtwo bending portions 21 a, is desirable for the elastic member. Needlessto say, U-shaped and V-shaped plate springs or coil springs may also beused if the foregoing problems do not matter.

[0224] Now, increasing a strut angle θ shown in FIG. 45 is effective atincreasing the torque capacity of the clutch while maintaining the outerdiameter dimension of the clutch. Here, the strut angle refers to anacute angle out of the interior angles of a triangle that is defined byconnecting the tangent points of the roller 20 on the circumferentialsurface 4 c 1 of the outer ring 4 and the cam surface 2 b 1 of theoutput shaft 2, and the center of the roller 20. When the strut angle θis increased, the roller 20 engaged into the wedge gap undergoes lowersurface pressure, which allows an increase in the torque capacity.Meanwhile, excessive strut angles θ can preclude the engagement of theroller 20 into the wedge gap and thus hamper the clutch function.Consequently, to obtain a sufficient torque capacity while securing theclutch function, the strut angle θ is favorably set within the range of3° and 4.5°, or yet preferably the range of 4° and 4.5°.

[0225] In the embodiment described above, the cam surface 2 b 1 of theoutput shaft 2 is a flat surface that makes a chord of a circumference,as shown enlarged in FIG. 46. When this cam surface 2 b 1 is formedconvex with the obtuse top of two tapered surfaces at the center asshown in FIG. 47, the spring space increases from L₃ to L₄ in size(L₃<L₄) even when the strut angle θ is the same as with the flat camsurface. This improves the design flexibility of the plate spring 21,allowing an increase in torque capacity resulting from higher rigidityof the plate spring 21 or the miniaturization of the clutch unitresulting from the reduced size of the plate spring 21. In this case,the taper angle φ between the two tapered cam surfaces 2 b 1 isdesirably set within the range of 1° and 5°.

[0226] The outer ring 1, the output shaft 2, the inner ring 3, the outerring 4, the first clutch part 5, the second clutch part 6, the fixingside plate 7, and the frictional member 9 described above are assembledas shown in FIG. 22 to complete the clutch unit of this embodiment. Theouter ring 1 is connected to an operation lever (13) made of resin, forexample. The output shaft 2 is connected to a rotating member of anot-shown output-side mechanism. Besides, the fixing side plate 7 isfixed to a fixing member such as a not-shown casing by caulking thecaulking portions 7 b 1. Incidentally, the outer ring 1 is restrainedbetween a washer (or nut) 18 attached to outside the collar portion 1 cand the flange portion 4 a of the outer ring 4 so as not to come offfrom either of the axial sides.

[0227] In the first clutch part 5, the centering spring 12 isaccommodated in the inner periphery of the protruding portions 1 a 2 ofthe outer ring 1, and restrained between one end face of the outer ring1 and the flange portion 4 a of the outer ring 4 so as not to come offfrom either of the axial sides. In addition, the retainer 11 and therollers 10 are restrained between the collar portion 1 c of the outerring 1 and the flange portion 4 a of the outer ring 4 so as not to comeoff from either of the axial sides. The retainer 11, the rollers 10, andthe centering spring 12 of the first clutch part 5 are accommodatedinside the outer ring 1 with no protrusion toward the input-side part.Moreover, the retainer 11 is mounted on the circumferential surface 3 a2 of the inner ring 3 so that the rotation of the retainer 11 is guidedby the circumferential surface 3 a 2 of the inner ring 3. The retainer11 can thus rotate without a tilt, allowing smooth clutch operation.

[0228] The second clutch part 6 is compactly accommodated in a spacesurrounded by the outer ring 4 and the fixing side plate 7 in radial andaxial directions. Besides, the column portions 3 c serving as the lockreleasing means and the pins 3 b 1 serving as the torque transmittingmeans are integrally arranged on the inner ring 3, with smaller partscount and simple structure. Moreover, the pockets 3 c 1 between thecolumn portions 3 c are shaped to open to an axial direction (toward theside plate 7). It is therefore possible to assemble the rollers 20 andthe plate springs 21 into the pockets 3 c 1 through the axial openingsof the pockets 3 c 1, after assembling the output shaft 2, the innerring 3, the outer ring 4, and the like, for easy assembly.

[0229] Furthermore, because of the structure for supporting the outputshaft 2 in a state of straddle with the radial bearing surface 3 a 1 ofthe inner ring 3 and the radial bearing surface 7 e 2 of the fixing sideplate 7, the output shaft 2 stabilizes in rotation. Besides, the firstclutch part 5 and the second clutch part 6 are less prone to partialload, allowing smooth clutch operation.

[0230] The clutch unit of this embodiment can be used in, for example,the seat-height-adjusting device 31 of the seat 30 shown in FIGS. 18 and19, as the clutch unit of the foregoing embodiment is.

[0231] Incidentally, an inner ring 3′ shown in FIG. 37 may be usedinstead of the inner ring 3 in the clutch unit of the foregoingembodiment. The inner ring 3′ shown in the diagram has a structure inwhich the cylindrical portion 3 a and the other portions (the portionsconsisting of the flange portion 3 b, the column portions 3 c, and thepins 3 b 1) are separated. The two portions are fixed by appropriatefixing means such as brazing. As compared to the inner ring 3 ofintegral structure, there is the advantage that precise fabrication ispossible at relatively low cost.

[0232] Otherwise, the input-side part alone may be configured as anindependent clutch unit in such form as shown in FIG. 48.

[0233]FIG. 49 shows a clutch unit which is the input-side part of theclutch unit (FIG. 54) according to a fifth embodiment of the presentinvention to be described later, exclusively configured as anindependent clutch unit.

[0234] This clutch unit comprises an outer ring 1′ as an input-sidemember, an inner ring 2′ as an output-side member, a plurality ofrollers 3′ as engaging members, a retainer 4′ for retaining the rollers3′, and an elastic member attached to the retainer 4, such as acentering spring 5′.

[0235] The outer ring 1′ is composed of a first thin member 1A′ shown inFIG. 50 and a second thin member 1B′ shown in FIG. 51. These thinmembers 1A′ and 1B′ are both fabricated by press-forming a steel plate.Incidentally, for example, the second thin member 1B′ may be made of amolded product of resin or the like if necessary.

[0236] The first thin member 1A′ comprises a cylindrical portion 1Ab′having a plurality of cam surfaces 1Aa′ formed on an inner peripherythereof at regular circumferential intervals, an inner flange portion1Ac′ extended inward from an end of the cylindrical portion 1 ab′, andan outer flange portion 1Ad′ extended outward from the other end of thecylindrical portion 1Ab′.

[0237] Each cam surface 1Aa′ is deep in its circumferential center, andgets shallower obliquely from the center toward both circumferentialsides. The inner flange portion 1Ac′ has the functions of restrainingthe retainer 4′ from coming off in an axial direction and maintainingthe outer ring 1′ coaxial to the inner ring 2′.

[0238] The outer flange portion 1Ad′ is provided with a plurality (six,in the shown example) of fitting grooves 1Ae′ intended for connectionwith the second thin member 1B′, and a plurality (three, in the shownexample) of stopper tabs 1Af′ axially extended from the outer end in adirection opposite from the cylindrical portion 1 ab′. In the directionof rotation, these stopper tabs 1Af′ are engaged with not-shown stopperprotrusions of a stationary-side member 7′ which is arranged on one side(right side in FIG. 49(a)) of the first thin member 1A′ with rotationconstraint, so that the rotation of the outer ring 1′ is restrainedwithin a predetermined range.

[0239] The entire first thin member 1A′ or the cam surfaces 1Aa′ aregiven heat treatment (surface hardening) such as carburizing andtempering, carbonitriding and tempering, induction hardening andtempering, or drip quenching and tempering.

[0240] As shown in FIG. 51, the second thin member 1B′ is provided witha plurality (six, in the shown example) of fitting tabs 1Ba′ axiallyextended from the outer end toward the first thin member 1A′. Thefitting tabs 1Ba′ are fitted in the fitting grooves 1Ae′ of the firstthin member 1A′ as shown in FIG. 52, so that both the thin members 1A′and 1B′ are restrained from relative rotation and axial relativemovement. Then, under this state, the fitting tabs 1Ba′ are engaged withprojections and depressions of an operation lever 6′ as an operatingmember to be mounted on the outer periphery. The operation lever 6′ isthus restrained from relative rotation with respect to the outer ring1′. Note that two short tabs 1Bb′ are formed in the shown example. Thesetabs 1Bb′ are not intended for connection with the first thin member 1A′(having the function of restraint on the direction of rotation alone).

[0241] A plurality (two, in the shown example) of burring portions 1Bc′axially extended toward the first thin member 1A′ are formed on theouter ends of the second thin member 1B′. Bolt through holes (or screwholes) 1Bd′ are formed in these burring portions 1Bc′, respectively.Through these holes 1Bd′, the operation lever 6′ is screwed to restrainthe axial relative movement of the operation lever 6′ with respect tothe outer ring 1′.

[0242] Consequently, when the operation lever 6′ is operated forrotation, the first thin member 1A′ and the second thin member 1B′rotate integrally so that the input torque from the operation lever 6′is input to the outer ring 1′. In addition, the inner ring 2′ has acircumferential surface 2 a′ for defining wedge gaps together with thecam surfaces 1Aa′ of the outer ring 1′ (the first thin member 1A′), andis connected to a not-shown output member.

[0243] As shown in FIG. 53, the retainer 4′ comprises a plurality (ten,for example) of window-like pockets 4 a′ for accommodating the rollers3′, and a engaged portion 4 b′ protruding in an axial direction from oneof the end faces. The engaged portion 4 b′ is formed in an arc shape,for example. Moreover, engaging portions of the centering spring 5′ areengaged with both circumferential sides 4 b 1′ and 4 b 2′ of the engagedportion 4 b′, respectively.

[0244] The material of the retainer 4′ is in conformity with the firstembodiment. Incidentally, in this example, the pocket 4 a′ adjoining toone of the circumferential sides 4 b 1′ and 4 b 2′ of the engagedportion 4 b′ is made smaller in axial dimension than the other pocket 4a′.

[0245] A clutch part 8′ comprises the cam surfaces 1Aa′ of the firstthin member 1A′ of the outer ring 1′, the circumferential surface 2 a′of the inner ring 2′, the retainer 4′ interposed between the camsurfaces 1Aa′ and the circumferential surface 2 a′, and the centeringspring 5′. Moreover, the cam surfaces 1Aa′, the circumferential surface2 a′, and the rollers 3′ constitute locking means. The retainer 4′ andthe centering spring 5′ constitute returning means.

[0246] The centering spring 5′ is the same as the centering spring 12shown in FIG. 32. Description will thus be omitted of the structure andoperation. The operation of the clutch part 8′ is also the same as inthe embodiment described before. Description thereof will thus beomitted.

[0247] According to this clutch unit, the outer ring 1′ serving as theinput-side member is fabricated by applying presswork to the twomembers, the first thin member 1A′ and the second thin member 1B′. Thisfacilitates the machining with a reduction in fabrication cost, andallows a reduction in the weight of the outer ring 1′ and by extensionthe clutch unit as compared to the case where the outer ring 1′ wereintegrally formed by cold forging or the like.

[0248] Moreover, while the first thin member 1A′ has the cam surfaces1Aa′ which are components of the clutch part, the second thin member 1B7has the fitting tabs 1Ba′ which are the connecting portions for theoperation lever 6′. The two members 1A′ and 1B′ thus differ in rigidityand hardness requirements. Applying surface hardening (heat treatment)to the first thin member 1A′ alone allows the individual characteristicrequirements to be met efficiently.

[0249]FIG. 54 shows a clutch unit according to a fifth embodiment of thepresent invention. The clutch unit according to this embodiment is thatthe clutch unit of the input-side part described above is integrallyunitized with an output-side clutch unit to be described below. Itcomprises an outer ring 1′ as an input-side member, an output shaft 12′as an output-side member, an inner ring 13′ as a control member, anouter ring 14′ as a stationary-side member, a first clutch part 15′arranged between the outer ring 1′ and the inner ring 13′, and a secondclutch part 16′ arranged between the outer ring 14′ and the output shaft12′.

[0250]FIG. 55 shows the output shaft 12′ as the output-side member. Theoutput shaft 12′ has a journal portion 12 a′ on one end, alarge-diameter portion 12 b′ at the center, and a connecting portion 12c′ on the other end. The journal portion 12 a′ is inserted in a radialbearing surface (13 a 1′) of the inner ring (13′: see FIG. 56) to bedescribed later. A plurality (eight, for example) of cam surfaces 12 b1′ are formed on the outer periphery of the large-diameter portion 12 b′at circumferential regular intervals. Each cam surface 12 b 1′ is formedinto a flat surface that makes a chord of a circle around the axialcenter of the output shaft 12′. A plurality (eight, for example) of pinholes 12 b 3′ are formed in one side of the large-diameter portion 12 b′at circumferential regular intervals. Pins (13 b 1′) of the inner ring(13′) are inserted in the pin holes 12 b 3′. Besides, an annular recess12 b 4′ is formed in the other side of the large-diameter portion 12 b′.A frictional member (19′: see FIG. 59) to be described later is pressedinto the annular recess 12 b 4′. Moreover, the inner peripheral wall 12b 5′ of the annular recess 12 b 4′ makes a journal surface to beinserted in a radial bearing surface (17 e 2′) of a fixing side plate(17′: see FIG. 58) to be described later. The connecting portion 12 c′is provided with a tooth profile 12 c 1′ intended for connecting toanother rotating member.

[0251] The output shaft 12′ is in conformity with the first embodimentin material, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the output shaft 12′).

[0252]FIG. 56 shows the inner ring 13′ as the control member. The innerring 13′ comprises a cylindrical portion 13 a′, a flange portion 13 b′extending outward from one end of the cylindrical portion 13 a′, and aplurality (eight, for example) of column portions 13 c′ extending in anaxial direction from the outer end of the flange portion 13 b′. Thecylindrical portion 13 a′ is mounted on the journal portion 12 a′ of theoutput shaft 12′, and inserted into the outer ring 1′. A radial bearingsurface 13 a 1′ for supporting the journal portion 12 a′ of the outputshaft 12′ radially is formed on the inner periphery of the cylindricalportion 13 a′ at the other end. A circumferential surface 13 a 2′ fordefining wedge gaps together with the cam surfaces 1Aa′ of the outerring 1′ in both the normal and reverse directions of rotation is formedon the outer periphery of the cylindrical portion 13 a′ at the otherend. A plurality (eight, for example) of pins 13 b 1′ protruding in anaxial direction are formed on the flange portion 13 b′ atcircumferential regular intervals. These pins 13 b 1′ are inserted inthe pin holes 12 b 3′ of the output shaft 12′, respectively. Pockets 13c 1′ opening to one axial direction are formed between the columnportions 13 c′ adjoining circumferentially. These pockets 13 c 1′accommodate rollers (30′) and plate springs (31′) of a second clutchpart (16′: see FIG. 61) to be described later. Since the rollers (30′)and the plate springs (31′) are loaded into the pockets 13 c 1′ throughthe axial openings of the pockets 13 c 1′, they are easy to assemble.

[0253] The inner ring 13′ is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the inner ring 13′).

[0254]FIG. 57 shows the outer ring 14′ as the stationary-side member.The outer ring 14′ comprises a flange portion 14 a′ extending radially,a cylindrical portion 14 c′ extending in one axial direction from theouter end of the flange portion 14 a′, and a collar portion 14 d′protruding outward from an end of the cylindrical portion 14 c′. Aplurality (two, for example) of stopper portions 14 a 1′ protruding inthe other axial direction are formed on the flange portion 14 a′ asarranged at predetermined circumferential intervals. These stopperportions 14 a 1′ are engaged with the stopper tabs 1Af′ of the outerring 1′ in the direction of rotation to restrain the range of rotationof the outer ring 1′. The flange portion 14 a′ is also provided with apair of engaged portions 14 a 2′ protruding in the other axial directionand a plurality (two, for example) of mounting portions 14 a 3′. Theengaging portions of the centering spring 5′ of the first clutch part(15′) are engaged with the circumferential outer sides of the pair ofengaged portions 14 a 2′, respectively. Besides, the winding portion ofthe centering spring 5′ is mounted on the outer periphery of themounting portions 14 a 3′.

[0255] A circumferential surface 14 c 1′ for defining wedge gapstogether with the cam surfaces 12 b 1′ of the output shaft 12′ in boththe normal and reverse directions of rotation is formed on the innerperiphery of the cylindrical portion 14 c′. A plurality (six, forexample) of notches 14 d 1′ are formed in the collar portion 14 d′ atpredetermined circumferential intervals. The notches 14 d 1′ match withcaulking portions (17 c′: see FIG. 58) of the fixing side plate (17′) tobe described later.

[0256] The outer ring 14′ is in conformity with the first embodiment inmaterial, the method of heat treatment, surface hardness, and so on(chromium molybdenum steel SCM 420 may be used as the material forforming the outer ring 14′).

[0257]FIG. 58 shows the fixing side plate 17′ to be fixed to the outerring 14′. The fixing side plate 17′ comprises a flange portion 17 a′extending radially, a plurality (four, for example) of bracket portions17 b′ protruding outward from the outer end of the flange portion 17 a′,a plurality (six, for example) of caulking portions 17 c′ protruding inone axial direction from the outer end of the flange portion 17 a′, aplurality (eight, for example) of engaging holes 17 a 1′ formed in theflange portion 17 a′, and a boss portion 17 e′ protruding in one axialdirection from the inner end of the flange portion 17 a′. The fourbracket portions 17 b′ are formed at predetermined circumferentialintervals, each having a caulking portion 17 b 1′ of hollow pin shapeformed integrally (or separately) therewith. The six caulking portions17 c′ are formed at predetermined circumferential intervals, each havinga pair of tabs 17 c 1′ branching in two. When these caulking portions 17c′ are fitted to the notches 14 d 1′ of the outer ring 14′ with thepairs of tabs 17 c 1′ caulked in circumferential opposite directionsinto contact with the collar portion 14 d′, so that the outer ring 14′can be prevented from axial relative movement and rotational relativemovement with respect to the fixing side plate 17′. The caulkingportions 17 b 1′ are fixed to the mounting holes of a mating member bycaulking.

[0258] A radial bearing surface 17 e 2′ is formed on the inner peripheryof the boss portion 17 e′. The boss portion 17 e′ is inserted in theannular recess 12 b 4′ of the output shaft 12′. The frictional member(19′: see FIG. 59) to be described later is attached to between theouter periphery of the boss portion 17 e′ and the outer peripheral wallof the annular groove 12 b 4′. The engaging holes 17 a 1′ are engagedwith projections (19 a′) of the frictional member (19′) in the directionof rotation, thereby preventing the relative rotation of the frictionalmember (19′) with respect to the fixing side plate 17′. The radialbearing surface 17 e 2′ of the boss portion 17 e′ is mounted on thejournal surface 12 b 5′ of the annular recess 12 b 4′ to support thejournal surface 12 b 5′ radially.

[0259] The fixing side plate 17′ is in conformity with the fourthembodiment in material, the method of formation, and the method of heattreatment.

[0260]FIG. 59 shows the frictional member 19′ as braking means. In thisembodiment, the frictional member 19′ has the shape of a ring, having aplurality (eight, for example) of projections 19 a′ formed on one of itsend faces at predetermined circumferential intervals. The projections 19a′ are engaged with the engaging holes 17 a 1′ of the fixing side plate17′ in the direction of rotation, thereby preventing the relativerotation of the frictional member 19′ with respect to the fixing sideplate 17′.

[0261] The frictional member 19′ is made of elastic material such asrubber and synthetic resin, and is pressed into the annular recess 12 b4′ of the output shaft 12′ with interference to the outer peripheralwall, for example. The frictional force occurring between the outerperiphery of the frictional member 19′ and the outer peripheral wall ofthe annular recess 12 b 4′ applies a braking force (frictional brakingforce) in the direction of rotation on the output shaft 12′. The settingof the braking force (braking torque) from the frictional member 19′ andthe material for forming the frictional member 19′ are in conformitywith the first embodiment.

[0262]FIG. 60 (B-B section of FIG. 54) shows the first clutch part 15′.The first clutch part 15′ comprises the plurality (ten, for example) ofcam surfaces 1Aa′ provided to the outer ring 1′, the circumferentialsurface 13 a 2′ provided to the inner ring 13′, a plurality (nine, forexample) of rollers 20′ as engaging members interposed between the camsurfaces 1Aa′ and the circumferential surface 13 a 2′, the retainer 4′for retaining the rollers 20′, and an elastic member for coupling theretainer 4′ to the outer ring (14′) in the direction of rotation, suchas the centering spring 5′. The cam surfaces 1Aa′, the circumferentialsurface 13 a 2′, and the rollers 20′ constitute locking means. Theretainer 4′ and the centering spring 5′ constitute returning means. Inthis embodiment, the cam surfaces 1Aa′ define wedge gaps together withthe circumferential surface 13 a 2′ in both the normal and reversedirections of rotation. Besides, an operation lever 23′ is connected tothe outer ring 1′. Input torque in the normal direction or reversedirection is input to the outer ring 1′ from the operation lever 23′.Moreover, grease is filled into the space between the inner periphery ofthe outer ring 1′ and the outer periphery of the inner ring 13′(cylindrical portion 13 a′), especially between the cam surfaces 1Aa′and the circumferential surface 13 a 2′ in particular.

[0263]FIG. 61 (A-A section of FIG. 54) shows the second clutch part 16′.The second clutch part 16′ comprises the circumferential surface 14 c 1′provided to the outer ring 14′, the plurality (eight, for example) ofcam surfaces 12 b 1′ provided to the output shaft 12′, a pair (a totalof eight pairs, for example) of rollers 30′ as engaging membersinterposed between each cam surface 12 b 1′ and the circumferentialsurface 14 c 1′, an elastic member interposed between the pair ofrollers 30′, such as an N-sectioned plate spring 31′, the columnportions 13 c′ of the inner ring 13′, the pins 13 b 1′ of the inner ring13′, and the pin holes 12 b 3′ of the output shaft 12′. The cam surfaces12 b 1′, the circumferential surface 14 c 1′, the pair of rollers 30′,and the plate spring 31′ constitute locking means. The column portions13 c′ of the inner ring 13′ lying on both circumferential sides of thepair of rollers 30′ constitute lock releasing means. The pins 13 b 1′ ofthe inner ring 13′ and the pin holes 12 b 3′ of the output shaft 12′constitute torque transmitting means. Moreover, grease is filled intothe space between the inner periphery of the outer ring 14 and the outerperiphery of the output shaft 12 (large-diameter portion 12 b),especially between the cam surfaces 12 b 1 and the circumferentialsurface 14 c 1 in particular. The operation of the second clutch part16′ is the same as in the embodiment described before. Descriptionthereof will thus be omitted.

[0264] The outer ring 1′, the output shaft 12′, the inner ring 13′, theouter ring 14′, the first clutch part 15′, the second clutch part 16′,the fixing side plate 17′, and the frictional member 19′ described aboveare assembled as shown in FIG. 54 to complete the clutch unit of thisembodiment. The outer ring 1′ is connected to the operation lever 23′made of resin, for example. The output shaft 12′ is connected to arotating member of a not-shown output-side mechanism. Besides, thefixing side plate 17′ is fixed to a fixing member such as a not-showncasing by caulking the caulking portions 17 b 1′. Incidentally, theouter ring 1′ is restrained between a washer (or nut) 28′ attached tooutside the second thin member 1B′ and the flange portion 14 a′ of theouter ring 14′ so as not to come off from either of the axial sides.

[0265] In the first clutch part 15′, the centering spring 5′ isaccommodated in the inner periphery of the stopper tabs 1Af′ of theouter ring 1′ (first thin member 1A′), and restrained between one endface of the outer ring 1′ and the flange portion 14 a′ of the outer ring14′ so as not to come off from either of the axial sides. In addition,the retainer 4′ and the rollers 20′ are restrained between the innerflange portion 1Ac′ of the outer ring 1′ and the flange portion 14 a′ ofthe outer ring 14′ so as not to come off from either of the axial sides.The retainer 4′, the rollers 20′, and the centering spring 5′ of thefirst clutch part 15′ are accommodated inside the outer ring 1′ with noprotrusion toward the input-side part. Moreover, the retainer 4 ismounted on the circumferential surface 13 a 2′ of the inner ring 13′ sothat the rotation of the retainer 4′ is guided by the circumferentialsurface 13 a 2′ of the inner ring 137. The retainer 4′ can thus rotatewithout a tilt, allowing smooth clutch operation.

[0266] The second clutch part 16′ is compactly accommodated in a spacesurrounded by the outer ring 14′ and the fixing side plate 17′ in radialand axial directions. Besides, the column portions 13 c′ serving as thelock releasing means and the pins 13 b 1′ serving as the torquetransmitting means are integrally provided to the inner ring 13′, withsmaller parts count and simple structure. Moreover, the pockets 13 c 1′between the column portions 13 c′ are shaped to open to one axialdirection (toward the fixing side plate 17′). It is therefore possibleto assemble the rollers 30′ and the plate springs 31′ into the pockets13 c 1′ through the axial openings of the pockets 13 c 1′, afterassembling the output shaft 12′, the inner ring 13′, the outer ring 14′,and the like, for easy assembly.

[0267] Furthermore, because of the structure for supporting the outputshaft 12′ in a state of straddle with the radial bearing surface 13 a 1′of the inner ring 13′ and the radial bearing surface 17 e 2′ of thefixing side plate 17′, the output shaft 12′ stabilizes in rotation.Besides, the first clutch part 15′ and the second clutch part 16′ areless prone to partial load, allowing smooth clutch operation.

[0268] Furthermore, the outer ring 1′ serving as the input-side memberis fabricated by applying presswork to the two members, the first thinmember 1A′ and the second thin member 1B′. This facilitates themachining with a reduction in fabrication cost, and allows a reductionin the weight of the outer ring 1′ and by extension the clutch unit.

[0269] While the first thin member 1A′ and the second thin member 1B′differ in rigidity or hardness requirement, the application of surfacehardening (heat treatment) to the first thin member 1A′ alone allows therespective requirements to be met efficiently.

[0270] The clutch unit of this embodiment can be used in, for example,the seat-height-adjusting device 31 of the seat 30 shown in FIGS. 18 and19, as the clutch unit of the above-described embodiment is.

[0271]FIG. 62 shows a clutch unit according to a sixth embodiment of thepresent invention. As compared to the fifth embodiment shown in FIG. 54,the clutch unit of this embodiment differs in the following structure.

[0272] As shown in FIG. 63, a retainer 4″ is cylindrical in shape, andcomprises a plurality (ten, for example) of window-like pockets 4 a″ foraccommodating rollers (3′) and a pair of openings 4 b″ spacedcircumferentially. The two openings 4 b″ have the shape of a windowclosed all around. Engaging portions 5 a 1″ and 5 a 2″ of an elasticmember 5″ to be described later are inserted in the openings 4 b″,respectively (see FIG. 66(a)).

[0273] As shown in FIG. 64, the elastic member 5″ is constituted byrolling metal strip material such as stainless steel into plate springs5A″ and 5B″ of cut ring shape, and laminating these two plate springs5A″ and 5B″. The engaging portions 5 a 1″ and 5 a 2″ are formed bybending inward the extremities of both ends of the inner plate spring5A″ at one axial side. The two engaging portions 5 a 1″ and 5 a 2″ arecircumferentially opposed to each other at a predetermined distance, andare inserted to the openings 4 b″ of the retainer 4″, respectively. Inaddition, engaged portions 5 b 1″ are formed by bending outward theextremities of the ends of the plate spring 5A″ at the other axial side.These engaged portions 5 b 1″ have the function of engaging with bothends of the outer plate spring 5B″, thereby restraining the plate spring5B″ from coming off or shifting in phase circumferentially. As shown inFIG. 65, the two engaged portions 5 b 1″ can be further bent away fromeach other to make the tilt angle θ acute so that the restrainingfunction is enhanced further.

[0274] To mount the elastic member 5″, as shown in FIG. 66(a){incidentally, the outer plate spring 5B″ is omitted from FIGS. 66(a)and 66(b) for the sake of simplicity of the drawings}, the engagingportions 5 a 1″ and 5 a 2″ are inserted to the openings 4 b″ of theretainer 4″, respectively, with the interval between the pair ofengaging portions 5 a 1″ and 5 a 2″ widened circumferentially so thatthe engaging portions 5 a 1″ and 5 a 2″ engage with circumferentialsides 4 b 1″ and 4 b 2″ of the openings 4 b″. The engaged portions 14 a2′ provided to the stationary-side member 14′ lie outside both the sides4 b 1″ and 4 b 2″. In the neutral position of the retainer 4″ shown inFIG. 66(a), both the engaging portions 5 a 1″ and 5 a 2″ of the elasticmember 5″ are also engaged with the engaged portions 14 a 2′. By theforegoing mounting, the retainer 4″ is coupled to the stationary-sidemember 14′ through the elastic member 5″ in the direction of rotation.

[0275] As shown in FIG. 66(d), when the retainer 4″ is relativelyrotated clockwise with respect to the stationary-side member from thisstate, the engaging portion 5 a 1″ lying in the clockwise direction(forward in the direction of rotation) of the engaging portions 5 a 1″and 5 a 2″ of the elastic member 5″ is pressed by the side 4 b 1″ of theretainer 4″ to make clockwise elastic displacement. At this point, theengaging portion 5 a 2″ of the elastic member 5″, lying in thecounterclockwise direction (backward in the direction of rotation), isengaged by the engaged portion 14 a 2′ of the stationary-side member14′. Consequently, the elastic member 5″ bends to the direction in whichthe interval between the pair of engaging portions 5 a 1″ and 5 a 2″ iswidened, so that the elastic member 5″ accumulates elastic forcecorresponding to the amount of bending. Subsequently, when the rotatingforce acting on the retainer 4″ is released, the retainer 4″ returns tothe neutral position shown in FIG. 66(a) by the elastic force of theelastic member 5″.

[0276] Incidentally, when the retainer 4″ is relatively rotatedcounterclockwise from the state shown in FIG. 66(a), the engagingportion 5 a 2″ of the elastic member 5″ in the counterclockwisedirection is pressed by the side 4 b 2″ of the retainer 4″ forcounterclockwise elastic displacement. The elastic member 5″ accumulateselastic force by the action reverse to the foregoing.

[0277] By the way, when the retainer 4″ is rotated as shown in FIG.66(b), stress distribution across the entire elastic member 5″ maybecome uneven. Then, the elastic member 4″ may bend irregularly withadverse effect. To avoid this, as shown in FIGS. 67(a) and 67(b), stressadjusting portions 5 c″ are desirably formed near both ends of the platesprings 5A″ and 5B″. The stress adjusting portions 5 c″ are intended toweaken the spring rigidity partially, and are constituted, for example,by forming holes in the plate spring 5A″ as shown in FIG. 67(a) or bycutting off both axial sides of the plate spring 5B″ as shown in FIG.67(b). No matter which of the stress adjusting portions 5 c″ is adopted,the plate springs 5A″, 5B″ shall be reduced in axial sectional areatoward the ends of the plate springs.

[0278] In FIGS. 67(a) and 67(b), the inner plate spring 5A″ is providedwith the holes, and the outer plate spring 5B″ is provided with the cutsas the stress adjusting portions 5 c″. On the contrary, the inner platespring 5A″ may be provided with the cuts, and the outer plate spring 5B″may be provided with the holes [see FIGS. 68(a) and 68(b)]. In thiscase, both the plate springs 5A″ and 5B″ may be provided with the sametype of stress adjusting portions 5 c″ (both are provided with theholes, or both are provide with the cuts). When the stress adjustingportions 5 c″ in both are holes, however, the inner side and the outerside of the elastic member 5″ can communicate through these holes tocause a drop in sealability (such as a bite of foreign material into theinner side of the elastic member 5″). It is therefore desirable thatcuts be adopted as the stress adjusting portions 5 c″ of at least eitherone (yet desirably the outer one) of the plate springs. Incidentally,the stress adjusting portions 5 c″ may be provided with both the platesprings 5A″ and 5B″ as described above, or in either one of the platesprings.

[0279] When the elastic member 5″ uses the plate springs 5A″ and 5B″ ofcut ring shape shown in FIGS. 64 to 68, it is possible to align theaxial positions of the engaging portions 5 a 1″ and 5 a 2″. Thisprecludes the retainer 4″ from moment load and thus enhances thereturning torque after rotative operations, so that the outer ring 1′and the operation lever can be surely restored to their neutralpositions.

[0280] To verify the foregoing effect, the clutch unit shown in FIG. 62and the clutch unit shown in FIG. 54 were individually measured for thetorque generated by the elastic member 5′, 5″ alone and the returningforce of the operation lever, followed by the calculation of thefrictional loss. The latter showed a generated torque of 170 [N·cm] anda returning force of 60 [N·cm] with a frictional loss of 110 [N·cm],whereas the former showed a generated torque of 110 [N·cm] and areturning force of 80 [N·cm] with a frictional loss of 20 [N·cm]. Thisverified that the frictional loss of the returning torque could bereduced significantly.

[0281] Now, when the elastic member 5″ uses the plate springs 5A″ and5B″ of cut ring shape, the openings 4 b″ formed in the retainer 41″ maybe identical in dimensions. This eliminates extremely thin portionsaround the openings 4 b″, thereby allowing an improvement in thestrength of the retainer 4″.

[0282] Incidentally, the number of plate springs to be used as theelastic member 5″ may be determined according to the returning torquerequired. It is therefore possible to use a single plate spring alone ora lamination of three or more springs, aside from the two springs asdescribed above. The number of plate springs for use can be thusmodified to adjust the returning torque easily.

[0283] Moreover, the outer ring 1′ serving as the input-side memberconsists of a first thin member 1A′ and a second thin member 1B′ as inthe embodiment shown in FIG. 54. In the embodiment shown in FIG. 54, theinner ends of the two members 1A′ and 1B′ are in close contact with eachother axially. In this embodiment, as shown in FIG. 62, the innerperiphery 1Be′ of an end of the second thin member 1B′ is arrangedaround the outer periphery of the first thin member 1A′, or moreparticularly, around the outer periphery of the inner flange portion1Ac′ so that end faces 1Ag′ and 1Bg′ of the two members 1A′ and 1B′ fallon an identical plane radially. Besides, an elastic member 29″consisting of a wavy spring or a disc spring is interposed between thewasher 28″ and the end face of the first thin member 1A′ to give anaxial preload to the outer ring 1′. As a result, wobbling of the outerring 1′ resulting from an initial gap of the clutch unit 15′ and thelike can be resolved to improve the feel of operation.

[0284] Incidentally, though omitted of illustration, only the input-sidepart of the clutch unit according to the sixth embodiment may beconfigured as an independent clutch unit in such form as shown in FIG.49.

[0285] By the way, in the neutral position of the second clutch part 6shown in FIG. 34 (the second clutch part 6 of the clutch unit accordingto the fourth embodiment shown in FIG. 22), for example, one of the pairof rollers 20 comes into wedged engagement with both the cam surface 2 b1 and the circumferential surface 4 c 1 by a relatively large engagingforce in response to the reverse input torque input to the output shaft2 from the side of the seat 30 (resulting from the empty weight of theseat 30 and the weight of the sitter). On that account, if the roller 20shows a high frictional force in coming out from the wedge gap (see FIG.35) by being pressed with the column portion 3 c of the inner ring 3, ahigh operating force may be required or the engaging part of the roller20 may cause vibrations or vibrating noise when the operation lever 31 a(13) is operated in a direction for lowering the position of the seat 30(hereinafter, the operation in this direction will be referred to as“down-operation”). In such cases, lubricating grease having a base oilviscosity of 750 cSt or above, such as “Multemp SH-Y” from Kyodo YushiCo., Ltd. (composed of base oil: PAO, thickener: Li-Ohst, additives:PTFE+special solid lubricant), can be filled into the second clutch part6 to solve the problem.

[0286]FIG. 69 shows the results of measurement on the occurrence ofvibrations when the operation lever 31 a (13) was subjected to thedown-operation and a returning action repeatedly with four types oflubricating grease differing in base oil viscosity alone (base oilviscosities of 100 cSt, 410 cSt, 750 cSt, and 1650 cSt) filled into thesecond clutch part 6 of the clutch unit according to the fourthembodiment. The horizontal axes are graduated in units of 5 sec. Thevertical axes show vibration acceleration. The vibration waveforms peakat instants when the rollers 20 come out from wedged engagement. Fromthe results shown in the diagram, it was confirmed that the values ofvibration levels decreased with the increasing base oil viscosity of thelubricating grease.

[0287]FIG. 70 is a diagrammatic representation of the correlationbetween the base oil viscosity and the vibration value (acceleration),on which averages of the vibration values at the respective base oilviscosities (FIG. 69) are plotted. Slight vibration or vibrating soundoccurring in the down-operation of the operation lever does notnecessarily matter when it falls within the allowable range such that itis imperceptive to the sitter or not unpleasant. As shown in thediagram, it was confirmed that the clutch units filled with lubricatinggrease having base oil viscosities of 750 cSt and above decreased towithin the allowable range of vibration values.

[0288] Incidentally, the foregoing effect becomes more significant whencoating treatment for friction reduction, such as phosphate coating,manganese phosphate coating, and solid lubricant coating is applied toat least one contact surface of the rolling contact surface of theroller 20, the circumferential surface 4 c 1 of the outer ring 4, andthe cam surface 2 b 1 of the output shaft 2. Moreover, the lubricatinggrease described above may be filled into not only the second clutchpart 6 but also the first clutch part 5.

[0289] As shown in FIG. 71, crowning 20 a may be applied to the rollingcontact surfaces of the rollers 20 of the second clutch part 6. Thissuppresses edge load at the contact portions with the rolling contactsurfaces of the rollers 20, promoting the formation of oil films by thelubricating grease. Incidentally, the rolling contact surfaces of therollers 10 of the first clutch part 5 may also be given the crowning.

[0290] Incidentally, the structure as to the lubricating grease and thesurface treatment (including the formation of crowning) described abovemay be applied to not only the fourth embodiment but all the foregoingembodiments as well.

What is claimed is:
 1. A clutch unit comprising: an input-side member towhich a torque is input; an output-side member from which a torque isoutput; a control member intervening in a torque transmission pathbetween the input-side member and the output-side member; astationary-side member constrained from rotation; a first clutch partarranged between the input-side member and the control member; and asecond clutch part arranged between the stationary-side member and theoutput-side member, wherein an input torque from the input-side memberis transmitted to the output-side member through the first clutch partand the control member, and a reverse input torque from the output-sidemember is locked with the stationary-side member through the secondclutch part.
 2. The clutch unit according to claim 1, wherein the firstclutch part comprises locking means for locking the input-side memberand the control member with respect to the input torque from theinput-side member, and returning means for returning the input-sidemember to a neutral position at which the input torque is not input whenthe input-side member is released.
 3. The clutch unit according to claim2, wherein the locking means comprises cam surfaces provided to theinput-side member, a circumferential surface provided to the controlmember, and engaging members interposed between the cam surfaces and thecircumferential surface, and wherein the returning means comprises aretainer for retaining the engaging members and an elastic member forcoupling the retainer with a non-rotating member in the direction ofrotation.
 4. The clutch unit according to claim 3, wherein thenon-rotating member is the stationary-side member.
 5. The clutch unitaccording to claim 3, wherein the stationary-side member has a stopperportion for restraining a range of rotation of the input-side member. 6.The clutch unit according to claim 3, wherein the engaging members, theretainer, and the elastic member are accommodated in the input-sidemember.
 7. The clutch unit according to claim 1, wherein the controlmember has a radial bearing portion for supporting the output-sidemember radially.
 8. The clutch unit according to claim 1, wherein thesecond clutch part comprises locking means for locking the output-sidemember and the stationary-side member with respect to the reverse inputtorque from the output-side member, lock releasing means for releasing alocked state due to the locking means with respect to the input torquefrom the input-side member, and torque transmitting means fortransmitting the input torque between the control member and theoutput-side member when the locked state due to the locking means isreleased.
 9. The clutch unit according to claim 8, wherein the lockingmeans comprises a circumferential surface provided to thestationary-side member, cam surfaces provided to the output-side memberfor defining wedge gaps together with the circumferential surface inboth normal and reverse directions of rotation, a pair of engagingmembers interposed between each of the cam surfaces and thecircumferential surface, and elastic members each of which presses thepair of engaging members toward the respective wedge gaps, and whereinthe lock releasing means comprises engaging elements for selectivelyengaging with either one of the pair of engaging members to press theengaging element toward the opposite direction of the wedge gap; andwherein the torque transmitting means comprises engaging elements in thedirection of rotation provided to the control member and the output-sidemember.
 10. The clutch unit according to claim 9, wherein the lockreleasing means and the torque transmitting means in a neutral positionhave a relationship of δ1<δ2, where δ1 is a rotational directionclearance between the engaging element of the lock releasing means andthe engaging member, and δ2 is a rotational direction clearance betweenthe engaging elements of the torque transmitting means.
 11. The clutchunit according to claim 9, wherein the lock releasing means is providedto the control member.
 12. The clutch unit according to claim 9, whereinthe torque transmitting means comprises projections provided to eitherone of the control member and the output-side member, and depressionsprovided to the other, the depressions conforming to the projections.13. The clutch unit according to claim 12, wherein the projection is apin provided to the control member, and the depression is a pin holeprovided to the output-side member.
 14. The clutch unit according toclaim 13, wherein the pin and the pin hole are provided in theclutch-axis direction.
 15. The clutch unit according to claim 1, furthercomprising a fixing side plate fixed to the stationary-side member. 16.The clutch unit according to claim 15, wherein the fixing side plate hasa radial bearing portion for supporting the output-side member radially.17. The clutch unit according to claim 1, further comprising brakingmeans for applying a braking force in the direction of rotation on theoutput-side member.
 18. The clutch unit according to claim 17, whereinthe braking means is interposed between the fixing side plate fixed tothe stationary-side member, or the stationary-side member, and theoutput-side member.
 19. The clutch unit according to claim 3, whereinthe elastic member of the first clutch part is formed of a torsion coilspring having a plurality of turns, individual winding centers being, ina natural state, offset to an opposite direction from a direction inwhich the individual winding centers shift accompany with increase inamount of operation of the retainer in an assembled state.
 20. Theclutch unit according to claim 19, wherein the individual windingcenters of the elastic member fall on the same axis when the retainer inthe assembled state is not in operation.
 21. The clutch unit accordingto claim 19, wherein the elastic member is of unwinding type.
 22. Theclutch unit according to claim 19, wherein the elastic member is shapedrectangular in section.
 23. The clutch unit according to claim 19,wherein the elastic member is wound with spacing between the winding.24. The clutch unit according to claim 15, wherein the fixing side plateis fixed to the stationary-side member by caulking.
 25. The clutch unitaccording to claim 24, wherein a caulking portion provided to the fixingside plate is bent for being caulked to the stationary-side member. 26.The clutch unit according to claim 25, wherein the caulking portion isbent in the circumferential direction of the stationary-side member. 27.The clutch unit according to claim 26, wherein the stationary-sidemember has a notch at an outer periphery thereof, the caulking portionis engaged with the notch.
 28. The clutch unit according to claim 27,wherein the caulking portion has a pair of tabs, the pair of tabs beingbent in opposite directions.
 29. The clutch unit according to claim 27,wherein the notch and the caulking portion are provided to thestationary-side member and the fixing side plate at a plurality ofcircumferential locations, respectively.
 30. The clutch unit accordingto claim 24, wherein the stationary-side member is made of hardenedsteel, and the fixing side plate is made of unhardened steel.
 31. Theclutch unit according to claim 9, wherein the elastic member of thesecond clutch part is formed of a plate spring having two bendingportions.
 32. The clutch unit according to claim 31, wherein the platespring has a coupling portion for coupling the two bending portions atone end each, and side plate portions extending from the other ends ofthe bending portions.
 33. The clutch unit according to claim 32, whereinthe cam surface provided to the output-side member is a flat surface ata portion on which the plate spring is mounted.
 34. The clutch unitaccording to claim 9, wherein the cam surface of the output-side memberis formed convex with two tapered surfaces.
 35. The clutch unitaccording to claim 34, wherein each of the tapered surfaces have a tiltangle of 1° to 5°.
 36. The clutch unit according to claim 35, whereinthe second clutch part has a strut angle of 3° to 4.5°.
 37. The clutchunit according to claim 3, wherein the elastic member of the firstclutch part has a pair of engaging portions differing from each other inthe axial position, and wherein the retainer has a pair of engagedportions with which the engaging portions of the elastic member engage,and pockets for retaining the engaging members, at least either one ofthe pair of engaged portions is axially thickened at a base partthereof.
 38. The clutch unit according to claim 37, wherein the pair ofengaged portions are formed of a notch respectively, a bottom of thenotch making one of the engaged portions lies closer to an end face ofthe retainer than a bottom of the notch making the other engagedportion.
 39. The clutch unit according to claim 38, wherein the one ofthe engaged portions is engaged with one of the pair of engagingportions of the elastic member lying closer to the end face of theretainer.
 40. The clutch unit according to claim 38, wherein the pocketis omitted near the base part of the other engaged portion.
 41. Theclutch unit according to claim 38, wherein the pocket is reduced inaxial dimension near the base part of the other engaged portion.
 42. Theclutch unit according to claim 40 or 41, wherein the other engagedportion is engaged with one of the pair of engaging portions of theelastic member lying closer to the center of the retainer.
 43. Theclutch unit according to claim 1, wherein the input-side member isformed by connecting a first thin member and a second thin member witheach other so as to be incapable of relative rotation, the first thinmember having the cam surfaces for the first clutch part, the secondthin member being connected with an operating member for inputting atorque.
 44. The clutch unit according to claim 43, wherein at leasteither one of the first thin member and the second thin member is of apress-formed product.
 45. The clutch unit according to claim 43, whereinthe first thin member and the second thin member are connected by adepression-projection fitting structure.
 46. The clutch unit accordingto claim 45, wherein either one of the first thin member and the secondthin member has a fitting tab, and the other has a groove portion withwhich the fitting tab is fit.
 47. The clutch unit according to claim 43,wherein at least the cam surfaces of the first thin member is appliedwith surface hardening.
 48. The clutch unit according to claim 3,wherein the elastic member of the first clutch part is formed of a platespring of cut ring shape.
 49. The clutch unit according to claim 48,wherein engaging portions capable of engagement with the retainer andthe stationary-side member, respectively, are formed at both ends of theelastic member.
 50. The clutch unit according to claim 49, wherein theengaging portions formed at both ends of the elastic member are arrangedat circumferentially opposite positions with each other.
 51. The clutchunit according to claim 49, wherein the retainer has openings capable ofengagement with the engaging portions of the elastic member, theopenings being closed all around.
 52. The clutch unit according to claim49, wherein stress adjusting portions are arranged near both ends of theelastic member.
 53. The clutch unit according to claim 48, wherein theelastic member is a lamination of two or more plate springs.
 54. Theclutch unit according to claim 53, wherein both ends of the inner sideplate spring are bent acute to form engaged portions, and both ends ofthe outer side plate spring are engaged with the engaged portions. 55.The clutch unit according to claim 8 or 9, wherein a lubricating greaseis applied to at least the interior of the second clutch part includingthe locking means, a base oil of the lubricating grease having aviscosity of 750 cSt or above.
 56. The clutch unit according to claim55, wherein a solid lubricant is added to the lubricating grease. 57.The clutch unit according to claim 56, wherein an extreme pressurelubricant is further added to the lubricating grease.
 58. The clutchunit according to claim 1, wherein the clutch unit is used in aseat-adjusting device of a motor vehicle.
 59. The clutch unit accordingto claim 58, wherein the input-side member is connected to an operationlever, and the output-side member is connected to a rotating member ofthe seat-adjusting device.
 60. The clutch unit according to claim 59,wherein the seat-adjusting device is a seat-height-adjusting device of asitting seat.